Ogling sweetheart in the French circle (7)
I believe the answer is:
leering
'ogling' is the definition.
(I've seen this before)
'sweetheart in the french circle' is the wordplay.
'sweetheart' becomes 'e' (the heart/centre of 'sweet').
'in' means one lot of letters goes inside another.
'the french' becomes 'le'.
'circle' becomes 'ring' ('ring' can be a synonym of 'circle').
'e' inserted into 'le' is 'lee'.
'lee'+'ring'='LEERING'
(Other definitions for leering that I've seen before include "Ogling" , "Looking suggestively" , "Gazing lasciviously" , "appearing lascivious" , "giving the glad eye" .)