A retiring person of little intelligence; a loner (5)
I believe the answer is:
aloof
'little intelligence a loner' is the definition.
I can't judge whether this defines the answer.
'a retiring person' is the wordplay.
'retiring' is a reversal indicator.
'person' becomes 'fool' (fool is a kind of person**).
'fool' written backwards gives 'loof'.
'a'+'loof'='ALOOF'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for aloof that I've seen before include "Unfriendly or distant like a fool" , "Showing detached attitude" , "Standing apart" , "Unpleasantly cold" , "Haughty and distant like a fool" .)