Small creature always invading rented property? (7)
I believe the answer is:
leveret
'small creature' is the definition.
(I know that leveret is a type of offspring)
'always invading rented property?' is the wordplay.
'always' becomes 'ever' (synonyms).
'invading' means one lot of letters goes inside another.
'rented property?' becomes 'let' (property to let).
'ever' placed within 'let' is 'LEVERET'.
(Other definitions for leveret that I've seen before include "youngster in form" , "Young hare" , "Young three dn" , "Fast runner, potentially" , "Young animal" .)