Topple American in overtime (4)
I believe the answer is:
oust
'topple' is the definition.
(thesaurus)
'american in overtime' is the wordplay.
'american' becomes 'US' (United States).
'in' indicates putting letters inside.
'overtime' becomes 'OT' (O and T are abbreviations for over and time).
'us' put within 'ot' is 'OUST'.
(Other definitions for oust that I've seen before include "Expel from office or position" , "Turf out" , "Get rid of" , "Remove from a position or office" , "Extract" .)