Weakness about love, say (5)
I believe the answer is:
voice
'say' is the definition.
(voicing is a kind of saying)
'weakness about love' is the wordplay.
'weakness' becomes 'vice' (I've seen this before).
'about' indicates putting letters inside.
'love' becomes 'o' (In tennis, 'love' means 'zero').
'vice' going around 'o' is 'VOICE'.
(Other definitions for voice that I've seen before include "Spoken sound" , "State" , "Opinion; express in words" , "eg Bass" , "right to have a say" .)