Scope for firm with a thousand to spend (7)
I believe the answer is:
compass
'scope' is the definition.
('compass' can be a synonym of 'scope')
'firm with a thousand to spend' is the wordplay.
'firm' becomes 'co' (a firm is a company).
'with' means one lot of letters go next to another.
'a thousand' becomes 'm' ('M' can be a synonym of 'thousand').
'to spend' becomes 'pass' ('pass' can be a synonym of 'spend').
'co'+'m'+'pass'='COMPASS'
'for' acts as a link.
(Other definitions for compass that I've seen before include "Range, extent" , "Direction finding instrument - range" , "Instrument for determining direction from magnetic needle" , "Orienteering instrument" , "Course guide" .)