Fancies gentleman surrounded by revolting offspring (7)
I believe the answer is:
desires
'fancies' is the definition.
(I've seen this in another clue)
'gentleman surrounded by revolting offspring' is the wordplay.
'gentleman' becomes 'sir' (a man may be addressed as sir).
'surrounded by' means one lot of letters goes inside another.
'revolting' is a reversal indicator.
'offspring' becomes 'seed' (I've seen this before).
'seed' backwards is 'dees'.
'sir' going into 'dees' is 'DESIRES'.
(Other definitions for desires that I've seen before include "needs" , "Wishes" , "Wants (7)." , "Covets and yearns for" , "Hopes" .)