Saw woman e.g. heading west (5)
I believe the answer is:
adage
'saw' is the definition.
(synonyms)
'woman e g heading west' is the wordplay.
'woman' becomes 'ada' ().
'heading west' says the letters should be written in reverse.
'e'+'g'='eg'
'eg' in reverse letter order is 'ge'.
'ada'+'ge'='ADAGE'
(Other definitions for adage that I've seen before include "Saw, proverb" , "Well-remembered proverb or saying" , "Old saying; proverb" , "Old saying, maxim" , "say it again and again!" .)