Level of public transport with more up front? (7)
I believe the answer is:
bustier
'with more up front?' is the definition.
(with a bigger bust)
'level of public transport' is the wordplay.
I cannot really see how this works, but
'level' could be 'tier' (synonyms) and 'tier' is located in the answer.
'transport' could be 'bus' (busing is a kind of transporting) and 'bus' is found in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for bustier that I've seen before include "For a lady, top" , "to climb in to tight clothing" , "Close-fitting, strapless top without sleeves" , "Heavier up top!" .)