Fish for Carl, meek, possibly (8)
I believe the answer is:
mackerel
'fish' is the definition.
(I know that mackerel is a type of fish)
'carl meek possibly' is the wordplay.
'possibly' is an anagram indicator.
'carl'+'meek'='carlmeek'
'carlmeek' is an anagram of 'MACKEREL'.
'for' is the link.
(Other definitions for mackerel that I've seen before include "Swimmer" , "Fish caught by spinner (or sprat?)" , "A food fish; type of sky" , "Common food fish" , "One in school" .)