Manor-house finally collapsed — son brought in workers in middle of week (7)
I believe the answer is:
demesne
'manor-house' is the definition.
(historical term for a farm with a manor)
'son brought in workers in middle of week' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'brought in' indicates putting letters inside.
'workers' becomes 'men' (men can mean staff or employees).
'in' indicates putting letters inside.
'middle of week' becomes 'dee' (I can't justify this - if you can you should believe this answer much more).
's' inserted into 'men' is 'mesn'.
'mesn' inserted into 'dee' is 'DEMESNE'.
'finally collapsed' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
(Other definitions for demesne that I've seen before include "Land attached to manor" , "Extensive landed property" , "Seed men (anag) -- land attached to a property and retained for the owner's personal use" , "Landed property used by the owner - needs me (anag)" , "Estate; sound like belittle" .)