I trade in the very best (5)
I believe the answer is:
ideal
'the very best' is the definition.
(I've seen this in another clue)
'i trade' is the wordplay.
'trade' becomes 'deal' (synonyms).
'i'+'deal'='IDEAL'
'in' acts as a link.
(Other definitions for ideal that I've seen before include "superb specimen" , "Exemplar" , "Model of perfection" , "Pattern" , "Optimal" .)