Lad keeping it working: are French workers to stay idle? (3,2,4,5)
I believe the answer is:
sit on ones hands
'stay idle?' is the definition.
(to sit on one's hands is to be idle)
'lad keeping it working are french workers' is the wordplay.
'lad' becomes 'son'.
'keeping' is an insertion indicator.
'working are french' becomes 'ones' (I can't explain this - if you can you should believe this answer much more).
'workers' becomes 'hands' (hand is a kind of worker).
'son' placed around 'it' is 'siton'.
'siton'+'ones'+'hands'='SIT ON ONES HANDS'
'to' acts as a link.
(Other definitions for sit on ones hands that I've seen before include "Refuse to act" , "fail to take action?" , "do nothing" .)