Pass out in mock attack, did you say? (5)
I believe the answer is:
faint
'pass out' is the definition.
(I know that pass out can be written as faint)
'mock attack did you say?' is the wordplay.
'mock attack' becomes 'feint' (I've seen this in another clue).
'did you say?' shows a homophone (sound like).
'feint' is a homophone of 'FAINT'.
'in' acts as a link.
(Other definitions for faint that I've seen before include "Hard to see" , "woozy" , "hard to hear" , "Indistinct - pass out" , "Dim -- swoon" .)