Restless wanderer has complaint about a fish (8)
I believe the answer is:
gadabout
'restless wanderer' is the definition.
'gadabout' can be an answer for 'wanderer' (thesaurus). I am not certain of the 'restless' bit.
'complaint about a fish' is the wordplay.
'complaint' becomes 'gout' (gout is a kind of health problem).
'about' indicates putting letters inside.
'fish' becomes 'dab' (dab is a type of fish).
'a'+'dab'='adab'
'gout' enclosing 'adab' is 'GADABOUT'.
'has' is the link.
Can you help me to learn more?
(Other definitions for gadabout that I've seen before include "restless sort" , "Person who goes around aimlessly" , "Pleasure-seeker" , "Vagrant" , "restless type" .)