Animal shelters in Mascot establishment (5)
I believe the answer is:
cotes
'animal shelters' is the definition.
(I've seen this in another clue)
'in mascot establishment' is the wordplay.
'in' indicates the answer is hidden within the clue.
'COTES' is hidden within 'mascot establishment'.
(Other definitions for cotes that I've seen before include "Shelters for pigeons" , "Dove or pigeon houses" .)