Enormous jab promises to include soldier (10)

I believe the answer is:

prodigious

'enormous' is the definition.
(thesaurus)

'jab promises to include soldier' is the wordplay.
'jab' becomes 'prod' (synonyms).
'promises' becomes 'IOUs' (promises to pay a debt).
'to include' is an insertion indicator.
'soldier' becomes 'GI' (GI can mean a US soldier).
'ious' going around 'gi' is 'igious'.
'prod'+'igious'='PRODIGIOUS'

(Another definition for prodigious that I've seen is " astonishing".)

I've seen this clue in The Daily Express.

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