In tennis, unsuccessfully hit Henman's returns, losing to love! (7)
I believe the answer is:
smitten
'in' is the definition.
Both the answer and definition are adjectives. Perhaps you can see a link between them that I don't see?
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for smitten that I've seen before include "Affected by something overwhelming" , "Besotted, enamoured" , "Severely afflicted" , "Very much in love" , "Much taken by" .)