US conscript must pack a coarse biscuit (9)
I believe the answer is:
garibaldi
'biscuit' is the definition.
(I've seen this before)
'us conscript must pack a coarse' is the wordplay.
'us conscript' becomes 'GI' (GI can mean a US soldier).
'must pack' means one lot of letters goes inside another.
'coarse' becomes 'ribald' (both can mean vulgar).
'a'+'ribald'='aribald'
'gi' going around 'aribald' is 'GARIBALDI'.
(Other definitions for garibaldi that I've seen before include "Italian hero, who led his 'Thousand Redshirts' against the Austrians, d. 1882" , "Blouse; biscuit; Italian patriot" , "Biscuit with currants" , "Currant biscuit - Italian patriot" , "Italian leader; biscuit" .)