Sombre Aussie soldier, one working in churchyard (11)
I believe the answer is:
gravedigger
'one working in churchyard' is the definition.
(someone who might work in a churchyard)
'sombre aussie' is the wordplay.
'sombre' becomes 'grave' (I've seen this before).
'aussie' becomes 'digger' (I can't justify this - if you can you should give a lot more credence to this answer).
'grave'+'digger'='GRAVEDIGGER'
'soldier' is the link.
Can you help me to learn more?
(Other definitions for gravedigger that I've seen before include "Sexton" , "working in churchyard?" , "One unearthing a plot" , "part in Hamlet" , "Cemetery worker" .)