Retentive beast born ugly (9)
I believe the answer is:
absorbent
'retentive' is the definition.
Both the definition and answer are adjectives. Perhaps you can see a link between them that I don't see?
'beast born ugly' is the wordplay.
'ugly' indicates an anagram.
'beast'+'born'='beastborn'
'beastborn' is an anagram of 'ABSORBENT'.
Can you help me to learn more?
(Other definitions for absorbent that I've seen before include "Sucking up liquid" , "Porous" , "Bob ran set (anag.)" , "Like a towel" , "Like a sponge" .)