Love racing? Could be natural (7)
I believe the answer is:
organic
'natural' is the definition.
(similar in meaning)
'love racing? could be' is the wordplay.
'love' becomes 'o' (love means zero in tennis).
'could be' is an anagram indicator.
'racing' anagrammed gives 'rganic'.
'o'+'rganic'='ORGANIC'
(Other definitions for organic that I've seen before include "Naturally grown" , "Formed from living things - no cigar for this one" , "Gin, Cora? (Anag)" , "Made from living matter" , "(Compound) containing carbon" .)