Universal poacher initially going in wears bears out (8)
I believe the answer is:
supports
'bears out' is the definition.
('support' can be a synonym of 'bear out')
'universal poacher initially going in wears' is the wordplay.
'initially' says to take the initial letters.
'going in' means one lot of letters goes inside another.
'wears' becomes 'sports' (sport can mean to wear or display on one's person).
The first letters of 'universal poacher' is 'up'.
'up' put into 'sports' is 'SUPPORTS'.
(Other definitions for supports that I've seen before include "Backs up, bears out" , "Bears the weight of" , "Holds up" , "Backs or approves of" , "Tees" .)