Come off worst in competition still (5-2)
I believe the answer is:
close-up
'come off worst' is the definition.
I can't tell whether this definition defines the answer.
'in competition still' is the wordplay.
'in' means one lot of letters goes inside another.
'competition' becomes 'cup' (I've seen this before).
'still' becomes 'lose' (I can't justify this - if you can you should give a lot more credence to this answer).
'cup' placed around 'lose' is 'CLOSE-UP'.
Can you help me to learn more?
(Other definitions for close-up that I've seen before include "Photograph giving a detailed view" , "Short-range photo" , "Photo giving detailed view, as of actor" , "Couples (anag.)" , "Shot of small area" .)