Misleading action is weak, by the sound of it (5)
I believe the answer is:
feint
'misleading action' is the definition.
(I've seen this before)
'weak by the sound of it' is the wordplay.
'weak' becomes 'faint' ('faint' can be similar in meaning to 'weak').
'by the sound of it' shows a homophone (sound like).
'faint' sounds like 'FEINT'.
'is' is the link.
(Other definitions for feint that I've seen before include "Misleading action" , "Deceptive motion" , "(Make a) deceptive move" , "Deceptive movement designed to distract" , "Pretended blow" .)