It's soul-destroying without getting on? Soldier is courageous! (5)
I believe the answer is:
gutsy
'courageous' is the definition.
('gutsy' can be a synonym of 'courageous')
'it's soul-destroying without' is the wordplay.
'soul-destroying' becomes 'guy' (I can't justify this - if you can you should give a lot more credence to this answer).
'without' indicates putting letters inside.
'ts' put into 'guy' is 'GUTSY'.
'getting on? soldier is' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for gutsy that I've seen before include "Courageous, spirited" , "Spirited; greedy" , "Sort of (non-standard)" , "Plucky" , "Brave" .)