Elbow say brownish, seen from underneath (5)
I believe the answer is:
nudge
'elbow' is the definition.
(I know this)
'say brownish seen from underneath' is the wordplay.
'say' becomes 'eg' (both can mean 'for example').
'brownish' becomes 'dun' (dun means of a brownish colour).
'seen from underneath' says the letters should be written in reverse (in a down clue, letters read from the bottom).
'eg'+'dun'='egdun'
'egdun' back-to-front is 'NUDGE'.
(Other definitions for nudge that I've seen before include "Jostle" , "Jogger" , "Light touch or push" , "Push (with a wink?)" , "Gentle push" .)