Nasty secret led hack to prepare for action (5,3,5)
I believe the answer is:
clear the decks
'prepare for action' is the definition.
(I've seen this before)
'nasty secret led hack' is the wordplay.
'nasty' indicates anagramming the letters.
'secret'+'led'+'hack'='secretledhack'
'secretledhack' is an anagram of 'CLEAR THE DECKS'.
'to' is the link.
(Other definitions for clear the decks that I've seen before include "Remove obstacles to action" , "Tidy up after card-games" , "Get shipshape - prepare for action" , "Tidy up all suits on hand to" , "Prepare for something by dealing first with matters outstanding" .)