Regular Irish assembly taking a key part (5)

I believe the answer is:

daily

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'regular' is the definition.
(similar in meaning)

'irish assembly taking a key part' is the wordplay.
'irish assembly' becomes 'dail' (I've seen this before).
'taking a key part' becomes 'y' (I can't justify this - if you can you should give a lot more credence to this answer).
'dail'+'y'='DAILY'

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(Other definitions for daily that I've seen before include "A rag, perhaps" , "Newspaper; cleaner" , "Cleaner; every 24 hours" , "Quotidian" , "Help" .)

I've seen this clue in the Evening Standard.

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