Set period at home filling legal document (10)
I believe the answer is:
determined
'set' is the definition.
('determined' can be a synonym of 'set')
'period at home filling legal document' is the wordplay.
'period' becomes 'term' (term is a kind of period**).
'at home' becomes 'in' ('in' can be similar in meaning to 'at home').
'filling' means one lot of letters goes inside another.
'legal document' becomes 'deed' (deed is a kind of legal document).
'term'+'in'='termin'
'termin' inserted into 'deed' is 'DETERMINED'.
(Other definitions for determined that I've seen before include "settled" , "firm" , "Decided - resolute" , "With full strength and concentration" , "set" .)