Nick’s old, mostly lazy (8)
I believe the answer is:
indolent
'lazy' is the definition.
(synonyms)
'nick's old mostly' is the wordplay.
I cannot really see how this works, but
an anagram of 'old' is 'dol' which is located in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for indolent that I've seen before include "Lethargic" , "Work-shy" , "Disinclined to exert oneself" , "Making no effort" , "Lazy, disinclined to work" .)