Bull and mare playing together in shelter (8)
I believe the answer is:
umbrella
'shelter' is the definition.
(I know that umbrella is a type of canopy)
'bull and mare playing together' is the wordplay.
'and' says to put letters next to each other.
'playing together' is an anagram indicator (letters play or mix together).
'bull'+'mare'='bullmare'
'bullmare' with letters rearranged gives 'UMBRELLA'.
'in' acts as a link.
(Other definitions for umbrella that I've seen before include "protective cover" , "Rain protector" , "cover for the British weather?" , "Handheld collapsible canopy" , "requirement in poor weather" .)