Trade is in it for a dreamer (8)
I believe the answer is:
idealist
'for a dreamer' is the definition.
('idealist' can be a synonym of 'dreamer')
'trade is in it' is the wordplay.
'trade' becomes 'deal' (synonyms).
'in' means one lot of letters goes inside another.
'deal'+'is'='dealis'
'dealis' put inside 'it' is 'IDEALIST'.
(Other definitions for idealist that I've seen before include "Dreamer" , "One has high hopes" , "An optimist or romantic" , "Perfectionist" , "Person with lofty and unselfish aspirations" .)