Optimistic husband to work on fuel problem (7)
I believe the answer is:
hopeful
'optimistic' is the definition.
(similar in meaning)
'husband to work on fuel problem' is the wordplay.
'husband' becomes 'h' (abbreviation).
'to work' becomes 'op' (abbreviation for opus).
'on' is an insertion indicator.
'problem' indicates anagramming the letters.
'fuel' anagrammed gives 'eful'.
'op' inserted inside 'eful' is 'opeful'.
'h'+'opeful'='HOPEFUL'
(Other definitions for hopeful that I've seen before include "Wannabe" , "Promising success" , "Prospect" , "Optimistic, expectant" , "One wishing to succeed" .)