Trouble inside — punch unwelcome visitor to house (7)
I believe the answer is:
bailiff
'unwelcome visitor to house' is the definition.
I can't tell whether this definition defines the answer.
'trouble inside punch' is the wordplay.
'trouble' becomes 'ail' (synonyms).
'inside' means one lot of letters goes inside another.
'punch' becomes 'biff' (synonyms).
'ail' inserted into 'biff' is 'BAILIFF'.
Can you help me to learn more?
(Other definitions for bailiff that I've seen before include "Court official" , "Landowner's agent" , "Law officer who helps sheriff, say to foreclose" , "Landlord's agent or steward" , "Sheriff's officer - landlord's agent" .)