Crossword Genius

No engagement for an army marching on its stomach! (5-2,5)

Ross

I believe the answer is:

stand-up fight

I'm a little stuck... Click here to teach me more about this clue!

'an army marching on its stomach' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.

'no engagement' is the wordplay.
'no' becomes 'standup' (I can't justify this - if you can you should believe this answer much more).
'engagement' becomes 'fight' (synonyms).
'standup'+'fight'='STAND UP FIGHT'

'for' is the link.

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I've seen this clue in The Irish News.
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