Got together again for just so long (5)

I believe the answer is:

metre

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'just so long' is the definition.
I can't judge whether this defines the answer.

'got together again' is the wordplay.
'got together' becomes 'met' ('meet' can be a synonym of 'get together').
'again' becomes 're' (prefix meaning 'again').
'met'+'re'='METRE'

'for' is the link.

Can you help me to learn more?

(Other definitions for metre that I've seen before include "39.37 inches" , "determined by scanning" , "Beat pattern (mus.)" , "Rhythmic arrangement of syllables in verse" , "Moisture remover" .)

I've seen this clue in the Evening Standard.

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