They deliver in half dozens (7)

I believe the answer is:

bowlers

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

'they' is the definition.
Both the definition and answer are plural nouns.
Maybe there's an association between them I don't understand?

'deliver in half dozens' is the wordplay.
'deliver' becomes 'bowl' (I've seen this before).
'in half dozens' becomes 'ers' (I am not sure about this - if you are sure you should believe this answer much more).
'bowl'+'ers'='BOWLERS'

Can you help me to learn more?

(Another definition for bowlers that I've seen is " Spinners maybe".)

I've seen this clue in the Evening Standard.

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