Desperate idiot driven occasionally to entertain soldiers (2-2-3)
I believe the answer is:
do-or-die
'desperate' is the definition.
('do or die' can describe a desperate situation)
'idiot driven occasionally to entertain soldiers' is the wordplay.
'occasionally' means one should take alternating letters (letters taken at regular intervals or occasions).
'to entertain' indicates putting letters inside.
'soldiers' becomes 'OR' (Other Ranks).
'idiot'+'driven'='idiotdriven'
The alternate letters of 'idiotdriven' are 'dodie'.
'dodie' placed around 'or' is 'DO-OR-DIE'.
(Other definitions for do-or-die that I've seen before include "Recklessly determined" , "Make a desperate effort whatever the consequences" , "Make a final desperate attempt to achieve" , "Showing a determination not to compromise" , "'Theirs not to reason why, theirs but to . . . . . . .' (2.2,3)" .)