Tired after force gets military order to assemble (6)

I believe the answer is:

fallin

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'military order to assemble' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'tired after force' is the wordplay.
'tired' becomes 'allin' (similar in meaning).
'after' says to put letters next to each other.
'force' becomes 'f' (scientific abbreviation).
'allin' put after 'f' is 'FALLIN'.

'gets' is the link.

Can you help me to learn more?

I've seen this clue in The Irish Times.

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