Both genders sustaining love, a great love for someone? (6)
I believe the answer is:
fandom
'love for someone?' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'both genders sustaining love a great' is the wordplay.
I cannot quite understand how this works, but
'love' could be 'o' (love means zero in tennis) and 'o' is located in the answer.
'a' could be 'an' and 'an' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for fandom that I've seen before include "Supporters generally" , "Enthusiasts" , "enthusiasm" , "Enthusiastically supportive followers" , "devotion" .)