Dine with attitude - imagine! (7)
I believe the answer is:
suppose
'imagine' is the definition.
(I know that imagine can be written as suppose)
'dine with attitude' is the wordplay.
'dine' becomes 'sup' (synonyms).
'with' means one lot of letters go next to another.
'attitude' becomes 'pose' (attitude can mean a pose or stance).
'sup'+'pose'='SUPPOSE'
(Other definitions for suppose that I've seen before include "Expect" , "Picture" , "Fancy" , "Guess" , "'Believe, perhaps on uncertain grounds (7)'" .)