Horse around what in Spain is a tent (7)
I believe the answer is:
marquee
'tent' is the definition.
(marquee is a kind of tent)
'horse around what in spain' is the wordplay.
'horse' becomes 'mare' (mare is a kind of horse).
'around' indicates putting letters inside.
'what in spain' becomes 'que' ('what' in Spanish).
'mare' going around 'que' is 'MARQUEE'.
'is a' acts as a link.
(Other definitions for marquee that I've seen before include "covering for hotel visitors there" , "Large tent used for party, exhibition etc" , "Tented pavilion" , "Elaborate tent" , "Canvas pavilion" .)