Seeing they help girls, give them a good start (7)

I believe the answer is:
glasses
'seeing they help' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'girls give them a good start' is the wordplay.
I cannot really understand how this works, but
'girls' could be 'lasses' (lass can informally mean a girl) and 'lasses' is found within the answer.
'good' could be 'g' (abbreviation) and 'g' is located in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for glasses that I've seen before include "Help in making out" , "Barnacles" , "Spectacles and receptacles" , "Small refracting telescopes" , "are they full of alcohol?" .)
