The little room is for him (5)
I believe the answer is:
denis
'him' is the definition.
'the little room is' is the wordplay.
'the little room' becomes 'den' (den is a kind of room. I am not sure about the 'little' bit.).
'den'+'is'='DENIS'
'for' is the link.
Can you help me to learn more?
(Other definitions for denis that I've seen before include "- Healey, former Chancellor of the Exchequer" , "Patron saint of France" , "St -, first Paris bishop" .)