Generous father in South Carolina promises to pay (8)
I believe the answer is:
spacious
'generous' is the definition.
(thesaurus)
'father in south carolina promises to pay' is the wordplay.
'father' becomes 'pa' (pa is a kind of father).
'in' indicates putting letters inside.
'south carolina' becomes 'sc'.
'promises to pay' becomes 'ious' (more than one iou).
'pa' going within 'sc' is 'spac'.
'spac'+'ious'='SPACIOUS'
(Other definitions for spacious that I've seen before include "wide-ranging" , "Having plenty of room" , "Roomy, not congested" , "Big and roomy" , "Roomy or expansive" .)