Takes up room in someone else's house (6)
I believe the answer is:
lodger
'takes up room in someone else's' is the definition.
I can't tell whether this definition defines the answer.
'house' is the wordplay.
I cannot quite see how this works, but
'house' could be 'lodge' (lodge is a kind of house) and 'lodge' is found within the answer.
A single letter 'r' remains which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for lodger that I've seen before include "Renter living with owner" , "One paying for accommodation" , "One who lives in a hired room" , "Renter sharing with the owner" , "He pays for room and board" .)