She shows zeal with no boy yet with love in her heart (3)
I believe the answer is:
zoe
'she' is the definition.
'with love in her heart' is the wordplay.
'with' says to put letters next to each other.
'love in' becomes 'zo' (I am not sure about this - if you are sure you should believe this answer much more).
'heart' means to look at the middle letters.
The middle letter of 'her' is 'e'.
'zo' next to 'e' is 'ZOE'.
'shows zeal with no boy yet' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for zoe that I've seen before include "Girl" , "___ Ball, broadcaster" , "Girl's name" .)