Pairs of lines set out across and down to start work (8)

I believe the answer is:

couplets

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

'pairs' is the definition.
('couplet' can be a synonym of 'pair')

I don't understand how the remainder of the clue works.

(Other definitions for couplets that I've seen before include "Pairs of consecutive lines of verse" , "Pairs of rhyming lines of verse" .)

I've seen this clue in The Irish Times.

Want a hint initially instead of a full solution? Install my app