Women wearing the same navy blue (4)
I believe the answer is:
down
'blue' is the definition.
(I've seen this before)
'women wearing the same navy' is the wordplay.
'women' becomes 'w'.
'wearing' is an insertion indicator.
'the same' becomes 'do' (abbreviation for ditto).
'navy' becomes 'n' (common abbreviation eg in RN Royal Navy).
'do'+'n'='don'
'w' placed within 'don' is 'DOWN'.
(Other definitions for down that I've seen before include "Rolling hill; soft feathers" , "Depressed; swallow" , "floor" , "Blue" , "Where this clue is going" .)