Time left at home with girl makes young horse (8)
I believe the answer is:
yearling
'young horse' is the definition.
(I've seen this before)
'time left at home with girl' is the wordplay.
'time' becomes 'year' (I've seen this in other clues).
'left' becomes 'l' (common abbreviation).
'at home' becomes 'in' (similar in meaning).
'with' says to put letters next to each other.
'girl' becomes 'g'.
'year'+'l'+'in'+'g'='YEARLING'
'makes' acts as a link.
(Other definitions for yearling that I've seen before include "Animal in its second year" , "Sort of racehorse" , "Young horse" , "Racehorse that is 12 months old" , "Animal in its second 12 months" .)