Firm beginning to repair attractive ornamental moulding (7)
I believe the answer is:
cornice
'ornamental moulding' is the definition.
(I've seen this before)
'firm beginning to repair attractive' is the wordplay.
'firm' becomes 'co' (a firm is a company).
'beginning to' indicates taking the first letters.
'attractive' becomes 'nice' ('nice' can be similar in meaning to 'attractive').
The first letter of 'repair' is 'r'.
'co'+'r'+'nice'='CORNICE'
(Other definitions for cornice that I've seen before include "Moulding between ceiling and top of a wall" , "Ornamental wall moulding" , "decorative part of room" , "Ledge of snow overhanging a precipice" , "Crane-fly" .)