Animal fancied occupying the back of your house (5)
I believe the answer is:
rhino
'animal' is the definition.
(I've seen this before)
'fancied occupying the back of your house' is the wordplay.
'fancied' becomes 'in' (as in fashionable).
'occupying' means one lot of letters goes inside another.
'the back of' indicates one should take the final letters.
'house' becomes 'ho' (abbreviation for house).
The final letter of 'your' is 'r'.
'r'+'ho'='rho'
'in' placed into 'rho' is 'RHINO'.
(Other definitions for rhino that I've seen before include "big game" , "endangered creature" , "Large animal (abbr) - money (slang)" , "one may charge unwary tourist?" , "Fierce beast (abbr.)" .)