Cry, having got old, weak and cowardly (6)
I believe the answer is:
yellow
'cowardly' is the definition.
('yellow' can be similar in meaning to 'cowardly')
'cry having got old weak' is the wordplay.
'cry' becomes 'yell' ('yell' can be a synonym of 'cry'**).
'having got' is a charade indicator (letters next to each other).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'weak' becomes 'w' (physics symbol as in W-boson).
'yell'+'o'+'w'='YELLOW'
'and' acts as a link.
(Other definitions for yellow that I've seen before include "Part of egg" , "like a canary" , "Primrose-coloured" , "Fearful - colour" , "Primary colour" .)