Protective cover's rolled up displaying fish (5)
I believe the answer is:
sprat
'fish' is the definition.
(I know that sprat is a type of herring)
'protective cover's rolled' is the wordplay.
'protective cover's' becomes 'tarp's' (short for 'tarpaulin').
'rolled' says the letters should be written in reverse (letters roll back).
'tarps' backwards is 'SPRAT'.
'up displaying' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for sprat that I've seen before include "Herring's smaller relative" , "Small edible fish" , "Strap up the small fish" , "Young herring" , "Parts of a very small fish" .)