Ace point to start complaint (5)
I believe the answer is:
tinea
'complaint' is the definition.
(tinea is a kind of health problem)
'ace point to start' is the wordplay.
'ace' becomes 'a' (abbreviation).
'point' becomes 'tine' (I've seen this in other clues).
'to start' is a charade indicator (letters next to each other).
'a' put after 'tine' is 'TINEA'.
(Other definitions for tinea that I've seen before include "skin infection" , "clothes moth" , "Skin complaint" , "Ringworm" , "Skin disease caused by a fungus" .)