I love model a little bit (4)
I believe the answer is:
iota
'little bit' is the definition.
(I've seen this in another clue)
'i love model a' is the wordplay.
'love' becomes 'o' (love means zero in tennis).
'model' becomes 'T' (Ford Model T car).
'i'+'o'+'t'+'a'='IOTA'
(Other definitions for iota that I've seen before include "Smidgeon" , "Gk. letter; tiny amount" , "Tiny or scarcely detectable amount" , "Smidgen" , "Ninth Greek character" .)