A visionary transaction is included in it (8)
I believe the answer is:
idealist
'a visionary' is the definition.
(I know that idealist is a type of visionary)
'transaction is included in it' is the wordplay.
'transaction' becomes 'deal' (a deal is a transaction or exchange).
'included in' indicates putting letters inside.
'deal'+'is'='dealis'
'dealis' placed inside 'it' is 'IDEALIST'.
(Other definitions for idealist that I've seen before include "Hopeful type" , "One has high hopes" , "One who pursues the perfect" , "Person striving for perfection" , "Person with high and unselfish standards" .)