Fish also swimming round husband (5)
I believe the answer is:
shoal
'fish' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'also swimming round husband' is the wordplay.
'swimming' indicates an anagram.
'round' is an insertion indicator.
'husband' becomes 'h'.
'also' with letters rearranged gives 'soal'.
'soal' going around 'h' is 'SHOAL'.
Can you help me to learn more?
(Other definitions for shoal that I've seen before include "Lots of fish" , "shallow water" , "Mob" , "Swarm of fish" , "A great number of fish swimming together" .)