I found this tough with good variety in clues - very enjoyable.
Solving time: 39 mins.

ACROSS
5 THES IS The Times Higher Education Supplement
11 BACK GROUND Reference to football in back, I think. This took me quite a while to get.
13 STOA First letters.
15 SE(R VAN)T Very good - the misleading surface distracted this solver for ages.
17 BOOKEND A cryptic definition I found quite quickly.
18 PROTEAN (a tenor p)*
19 SOLDIER Serve (soldier is a vb)
21 (t)RUTH "Beauty is truth, truth beauty" from Keats' poem Ode to a Grecian Urn. "Not the first time" means take away the first t.
25 ITALIAN VERMOUTH (at home in virtual)* Definition = It Excellent.

DOWN
1 CELEB(E)S New to me, but I got it from the clear wordplay. It's in Indonesia.
4 CAIRO (?) It's an African capital, but I was expecting perhaps Chi and something else in the wordplay, but can see nothing. Help appreciated.
8 STEW A RD
9 STANDBYS partnership = stand (cricket) "buys" homophone.
14 NO BLEW OMEN blow = leave so blew = left
16 TAN (beat) GOING The "with" means the parts can be in either order
18 PART (IT) A It in part A (the first section)
20 ROSE HIP Hip = with it
26 UK E

Testing one, two

Standing in for one of the regulars for my first Times Community review, this was an accessible puzzle.
As a daily Indy solver, have been doing the Times almost every day only in fairly recent times. Solved in 28 mins, this is reasonably good for me for the Times.

* = anagram

ACROSS
1 F ACTOR When I found the answer, I was disappointed I did not get this more quickly but was misled by "One to be taken into" into looking for a container.
4 A KIT SAWS (all reversed) - a bit surprised to see this word with all its assocations included in the puzzle.
10 COUNTRYSIDE Countrywide (Coast-to-coast) with s for w. Easy, I thought.
12 (Stable)LAD + DISH (a smasher) - slang I have not heard for a while.
15 F LIGHT SERGE ANT
21 ASHIEST shies = pitches(throws) in edges of AsphalT (first and last letters). Reminding the night-time viewers of the uphill struggle in Oz?
23 OAF My favourite clue, telling us to "Sort" (of a)*. Did I see it straightaway? Most certainly not. Jonathan Swift's Yahoo, nothing to do with the Internet.
24 NIKKEI INDEX - Japanese equivalent of the FTSE. Anagram of One = I and "keen kid in" + X = vote as you would on a ballot paper.
27 GENEVA (avenge)*. WHO and many international organisations with HQs there, many in buildings that housed the League of Nations between the wars.

DOWN
1 FACE-LIFT life "set up" in fact. Liked it.
2 CRU "Noisy" means a homophone (of crew)
8 AGREED a greed. Nice
16 ANOREXIA extremely rare = first and last letters (re) in anoxia. Familiar word (the answer, that is).
19 AGONISE last word I filled in and I, well, agonised, over it. Thought of it early on but could not quite see it as equivalent to "labour". Finally, convinced by the wordplay - Leaders i.e. first letters of international standing (IS) in a = are (metric square measure) + left = gone.
20 SAVO(I)UR "Ignoring" one = I
25 DYE Liked this a lot. Definition is not colour but change colour. D'ye? = Do you?