Cowardly son unfortunately sleeps in (9)
I believe the answer is:
spineless
'cowardly' is the definition.
(I've seen this before)
'son unfortunately sleeps in' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'unfortunately' indicates anagramming the letters (a bad or unfortunate spelling).
'sleeps'+'in'='sleepsin'
'sleepsin' anagrammed gives 'pineless'.
's'+'pineless'='SPINELESS'
(Other definitions for spineless that I've seen before include "Not like Mrs Tiggy-Winkle" , "Craven, lacking vertebrae" , "Yellow" , "Lily-livered" , "Weak, purposeless" .)