Words of love among sisters (5)
I believe the answer is:
nouns
'words' is the definition.
(noun is a kind of word)
'love among sisters' is the wordplay.
'love' becomes 'o' (love means zero in tennis).
'among' means one lot of letters goes inside another.
'sisters' becomes 'nuns' (I've seen this in another clue).
'o' inserted inside 'nuns' is 'NOUNS'.
'of' is the link.
(Other definitions for nouns that I've seen before include "They can be used to refer to persons, places or things" , "Naming words" , "Identifying words" , "Words of particular type" , "Parts of speech" .)