Deep red jumper chap's shut away (6)
I believe the answer is:
maroon
'deep red' is the definition.
(I've seen this in another clue)
'jumper chap's shut away' is the wordplay.
'jumper' becomes 'roo' (I've seen this before).
'chap' becomes 'man' (chap can mean a man).
'shut away' means one lot of letters goes inside another.
'roo' placed within 'man' is 'MAROON'.
(Other definitions for maroon that I've seen before include "castaway?" , "Source of report" , "Purplish colour" , "Brownish-crimson - abandon ashore" , "Dark brownish-red" .)