Does fast pass on street heading west (5)
I believe the answer is:
diets
'does fast' is the definition.
(dieting is a kind of fasting)
'pass on street heading west' is the wordplay.
'pass' becomes 'die' (I've seen this before**).
'on street' becomes 'st' (I've seen this in other clues).
'heading west' is a reversal indicator.
'st' in reverse letter order is 'ts'.
'die'+'ts'='DIETS'
(Other definitions for diets that I've seen before include "Regimens" , "Commons" , "causing stones to vanish" , "Legislative assemblies" , "Tides (anag.)" .)