Girls left by silly fellows? (6)
I believe the answer is:
lasses
'girls' is the definition.
(lass can mean a girl)
'left by silly fellows?' is the wordplay.
'left by' becomes 'l' (I've seen this in other clues).
'silly fellows?' becomes 'asses' (I can't explain this - if you can you should believe this answer much more).
'l'+'asses'='LASSES'
Can you help me to learn more?
(Other definitions for lasses that I've seen before include "Northern girls?" , "Young ladies" , "Lads and - -" .)