Execute second lag (4,4)
I believe the answer is:
hang back
'lag' is the definition.
(hanging back is a kind of lagging)
'execute second' is the wordplay.
'execute' becomes 'hang' (hanging is a kind of executing).
'second' becomes 'back' (to second a motion is to back it).
'hang'+'back'='HANG BACK'
(Other definitions for hang back that I've seen before include "Get behind" , "Remain behind" , "Show reluctance" .)