Home pet, terribly clumsy (5)
I believe the answer is:
inept
'clumsy' is the definition.
('inept' can be a synonym of 'clumsy')
'home pet terribly' is the wordplay.
'home' becomes 'in' ('he's home' can mean 'he's in').
'terribly' indicates an anagram.
'pet' is an anagram of 'ept'.
'in'+'ept'='INEPT'
(Other definitions for inept that I've seen before include "Blundering" , "Lacking skill" , "Unskilful, awkward" , "Amateurish" , "Clumsy, bungling" .)