Trendy exploit? Absolutely (6)
I believe the answer is:
indeed
'absolutely' is the definition.
(both can be used to agree with something)
'trendy exploit?' is the wordplay.
'trendy' becomes 'in' ('in' can mean fashionable).
'exploit?' becomes 'deed' (both can mean a feat or escapade).
'in'+'deed'='INDEED'
(Other definitions for indeed that I've seen before include "Truly or admittedly" , "Surely" , "Actually -- denied (anag)" , "Certainty" , "Really; certainly" .)