Greet workers led by wag (5,5)
I believe the answer is:
shake hands
'greet' is the definition.
(shaking hands is a kind of greeting)
'workers led by wag' is the wordplay.
'workers' becomes 'hands' (hand is a kind of worker).
'led by' says to put letters next to each other.
'wag' becomes 'shake' ('shake' can be a synonym of 'wag').
'hands' put after 'shake' is 'SHAKE HANDS'.
(Other definitions for shake hands that I've seen before include "Greet" , "Finalise agreement" .)