First to last in contest? That's horrible (4)
I believe the answer is:
vile
'horrible' is the definition.
(I've seen this before)
'first to last in contest?' is the wordplay.
'first to' says to take the initial letters.
'in' is an insertion indicator.
'contest?' becomes 'vie' (I've seen this before).
The initial letter of 'last' is 'l'.
'l' inserted inside 'vie' is 'VILE'.
'that's' is the link.
(Other definitions for vile that I've seen before include "Horrible" , "___ Bodies, Evelyn Waugh's 1930 novel" , "Extremely unpleasant" , "Despicable in evil way" , "Disgusting, quite evil" .)