If `iresting^i, he has nothing to cart around (5)
I believe the answer is:
actor
'if 'irestingi he' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'nothing to cart around' is the wordplay.
'nothing' becomes 'O' (looks like zero - 0).
'around' is an anagram indicator.
'o'+'cart'='ocart'
'ocart' is an anagram of 'ACTOR'.
'has' is the link.
Can you help me to learn more?
(Other definitions for actor that I've seen before include "one to take on roles" , "Theatrical performer" , "Films/stage worker" , "Stage player" , "ham" .)