There's little room on an island for him (5)
I believe the answer is:
denis
'there's little room on an island for him' is the definition.
The definition suggests a singular noun which matches the answer.
'island for him' is the wordplay.
'island' becomes 'is' (abbreviation).
'for' means one lot of letters go next to another (I've seen this in other clues).
'him' becomes 'den' ().
'is' put after 'den' is 'DENIS'.
Can you help me to learn more?
(Other definitions for denis that I've seen before include "St -, first Paris bishop" , "- Healey, former Chancellor of the Exchequer" , "Patron saint of France" .)