Young creatures always invading rented properties (8)
I believe the answer is:
leverets
'young creatures' is the definition.
'leverets' can be an answer for 'creatures' (I have seen 'small creatures' mean 'leverets' so perhaps 'creatures' could also mean 'leverets'). I am not certain of the 'young' bit.
'always invading rented properties' is the wordplay.
'always' becomes 'ever' (synonyms).
'invading' indicates putting letters inside.
'rented properties' becomes 'lets' (I can't justify this - if you can you should believe this answer much more).
'ever' put into 'lets' is 'LEVERETS'.
Can you help me to learn more?
(Other definitions for leverets that I've seen before include "big-eared youngsters" , "Set elver among young hares" , "Set elver to get young hares" , "small creatures" , "Let verse envisage young hares" .)