Empty the American packs ready for action (5,3,5)
I believe the answer is:
clear the decks
'ready for action' is the definition.
'clear the decks' can be an answer for 'ready' (thesaurus). I am unsure of the 'for action' bit.
'empty the american packs' is the wordplay.
'empty' becomes 'clear' (I've seen this before).
'american packs' becomes 'decks' (deck is a kind of pack. I am not sure about the 'american' bit.).
'clear'+'the'+'decks'='CLEAR THE DECKS'
Can you help me to learn more?
(Other definitions for clear the decks that I've seen before include "Get ready for action" , "Get shipshape - prepare for action" , "Prepare for something by dealing first with matters outstanding" , "Prepare for action - these crackled (anag)" , "prepare for new action" .)