Lets off about American conflict (6)
I believe the answer is:
tussle
'conflict' is the definition.
(tussle is a kind of conflict)
'lets off about american' is the wordplay.
'off' is an anagram indicator.
'about' is an insertion indicator.
'american' becomes 'us'.
'lets' is an anagram of 'tsle'.
'tsle' going around 'us' is 'TUSSLE'.
(Other definitions for tussle that I've seen before include "Struggle like wrestling bout" , "A struggle or conflict" , "Sharp struggle" , "Vigorous struggle or scuffle" , "Brawl" .)