“Very little in street” — hear Tom’s first girlfriend (10)
I believe the answer is:
sweetheart
'girlfriend' is the definition.
(I've seen this before)
'very little in street hear tom's first' is the wordplay.
'very little' becomes 'wee' (I've seen this in another clue).
'in' is an insertion indicator.
'street' becomes 'st' (abbreviation).
'tom's first' becomes 't' (1st letter of 'tom').
'wee' inserted within 'st' is 'sweet'.
'sweet'+'hear'+'t'='SWEETHEART'
(Other definitions for sweetheart that I've seen before include "Beloved" , "Term of endearment" , "baby" , "Darling" , "Dear" .)