Drive second, going over flag (4)
I believe the answer is:
spin
'drive' is the definition.
(thesaurus)
'second going over flag' is the wordplay.
'second' becomes 's' (common abbreviation).
'going over' says to put letters next to each other.
'flag' becomes 'pin' ('pin' can be a synonym of 'flag').
's'+'pin'='SPIN'
(Other definitions for spin that I've seen before include "Short pleasure trip" , "Make thread; go round" , "Toss" , "This doctor deals in political publicity" , "Rotate; ride" .)