Muscle pigs displayed, moving west (5)
I believe the answer is:
sinew
'muscle pigs' is the definition.
'sinew' can be an answer for 'muscle' (I've seen this before). I'm unsure of the 'pigs' bit.
'displayed moving west' is the wordplay.
'displayed moving' becomes 'sine' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'west' becomes 'W' (abbreviation).
'sine'+'w'='SINEW'
(Other definitions for sinew that I've seen before include "As synonym for 'strength'" , "power source" , "It indicates strength" , "Tough material" , "Cord of tissue connecting muscle to bone" .)