Great love omitted from last letter (4)
I believe the answer is:
mega
'great' is the definition.
(I've seen this before)
'love omitted from last letter' is the wordplay.
'love' becomes 'o' (love means zero in tennis).
'omitted from' is a deletion indicator.
'last letter' becomes 'omega' (I've seen this before).
'omega' with 'o' removed is 'MEGA'.
(Other definitions for mega that I've seen before include "Smashing" , "wicked" , "Very large (prefix)" , "Great American" , "ace" .)