A swine blocking a good deal for timber (8)
I believe the answer is:
mahogany
'for timber' is the definition.
(I have seen 'Tropical timber' mean 'mahogany' so perhaps 'timber' could also mean 'mahogany')
'a swine blocking a good deal' is the wordplay.
'swine' becomes 'hog' (hog is a kind of swine).
'blocking' indicates putting letters inside (block can mean to plug a gap in something).
'a good deal' becomes 'many'.
'a'+'hog'='ahog'
'ahog' going within 'many' is 'MAHOGANY'.
(Other definitions for mahogany that I've seen before include "Reddish-brown hardwood" , "Hard tropical wood used in making furniture" , "Type of wood" , "Old Cornish drink" , "Reddish-brown wood" .)