Fish or hen sits on it (5)
I believe the answer is:
perch
'fish' is the definition.
(I know that perch is a type of fish)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for perch that I've seen before include "[SOMETHING FISHY]" , "bird comes down on" , "Freshwater fish - roost" , "Bird's seat - fish" , "Bird's roost" .)