Extremely trendy suit (2,6)
I believe the answer is:
in spades
'extremely' is the definition.
(I've seen this in another clue)
'trendy suit' is the wordplay.
'trendy' becomes 'in' ('in' can mean fashionable).
'suit' becomes 'spades' (playing card suit).
'in'+'spades'='IN SPADES'
(Other definitions for in spades that I've seen before include "To a very great degree" , "Decidedly" , "Where a contract may be made" , "Without restraint" , "how a contract may be agreed" .)