Just think: I resolved enigma! (7)
I believe the answer is:
imagine
'just think' is the definition.
(I've seen this in another clue)
'i resolved enigma' is the wordplay.
'resolved' is an anagram indicator.
'enigma' with letters rearranged gives 'magine'.
'i'+'magine'='IMAGINE'
(Other definitions for imagine that I've seen before include "Picture in mind, envisage" , "Assume" , "Reckon" , "Picture, conceive" , "Enigma, I? (anag)" .)