It's a sign of love, chaps (4)
I believe the answer is:
omen
'it's a sign' is the definition.
(omen is a kind of sign)
'love chaps' is the wordplay.
'love' becomes 'o' (love means zero in tennis).
'chaps' becomes 'men' (I've seen this before).
'o'+'men'='OMEN'
'of' is the link.
(Other definitions for omen that I've seen before include "Gloomy sign" , "Portent of evil" , "Portent of things to come" , "Forecast" , "writing on the wall" .)