Hang about, there's nothing in the measure of an American (6)
I believe the answer is:
loiter
'hang about' is the definition.
(thesaurus)
'nothing in the measure of an american' is the wordplay.
'nothing' becomes 'o' (looks like zero - 0).
'in the' indicates putting letters inside.
'measure of an american' becomes 'liter' (US spelling of 'litre').
'o' inserted inside 'liter' is 'LOITER'.
'there's' is the link.
(Other definitions for loiter that I've seen before include "Wait suspiciously" , "Skulk" , "Linger, with intent perhaps" , "lounge" , "Hang about, with 25 dn perhaps" .)