Senseless state positions retreating troops (6)
I believe the answer is:
'senseless state' is the definition.
'positions retreating troops' is the wordplay.
'positions' becomes 'puts' ('put' can be a synonym of 'position').
'retreating' says the letters should be written backwards.
'troops' becomes 'or' (military abbreviation for other ranks).
'puts' back-to-front is 'stup'.
(Other definitions for stupor that I've seen before include "Semi-comatose state" , "Dazed condition as from drink or drugs" , "State of insensibility or near-unconsciousness" , "numbness" , "mental dullness?" .)