Is he the sort to laze? Unlikely! (6)
I believe the answer is:
zealot
'is he the sort' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'to laze? unlikely' is the wordplay.
'unlikely' indicates an anagram (an unlikely spelling of the letters).
'to'+'laze'='tolaze'
'tolaze' anagrammed gives 'ZEALOT'.
Can you help me to learn more?
(Other definitions for zealot that I've seen before include "Fanatic, fiery follower" , "Radical" , "Fanatic, obsessed person" , "Fanatic, usually religious" , "A fanatic or obsessed follower" .)