Ian's confused with love for a girl (5)
I believe the answer is:
sonia
'girl' is the definition.
(woman's name)
'ian's confused with love' is the wordplay.
'confused with' indicates anagramming the letters.
'love' becomes 'o' (love means zero in tennis).
'ians' mixed up with 'o' makes 'SONIA'.
'for a' is the link.
(Other definitions for sonia that I've seen before include "Noa is really a girl" , "...O'Sullivan, great Irish athlete" .)