Attack American president receiving head from Monica (6)
I believe the answer is:
ambush
'attack' is the definition.
(ambush can mean to attack suddenly)
'american president receiving head from monica' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'president' becomes 'bush' (George H W Bush or George W Bush).
'receiving' means one lot of letters goes inside another.
'head from' suggests taking the first letters.
The first letter of 'monica' is 'm'.
'a'+'bush'='abush'
'abush' going around 'm' is 'AMBUSH'.
(Other definitions for ambush that I've seen before include "Lie in wait; trap" , "Launch attack from cover" , "spring a trap" , "Waylay" , "Lying in wait to attack" .)