Pound is small, housing single feline (7)
I believe the answer is:
lioness
'feline' is the definition.
(lioness is a kind of feline)
'pound is small housing single' is the wordplay.
'pound' becomes 'l'.
'small' becomes 's' (abbreviation - e.g. clothes size).
'housing' is an insertion indicator.
'single' becomes 'one' (I've seen this before).
'is'+'s'='iss'
'iss' placed around 'one' is 'ioness'.
'l'+'ioness'='LIONESS'
(Other definitions for lioness that I've seen before include "Large cat" , "predatory female'" , "Predator" , "Female pride member" , "Female big cat" .)