Perhaps cramp lookalike, say, heading west (6)
I believe the answer is:
twinge
'perhaps cramp' is the definition.
(twinge of pain)
'lookalike say heading west' is the wordplay.
'lookalike' becomes 'twin' (twin can mean a lookalike).
'say' becomes 'eg' (both can mean 'for example').
'heading west' says the letters should be written backwards.
'eg' backwards is 'ge'.
'twin'+'ge'='TWINGE'
(Other definitions for twinge that I've seen before include "Emotional pang" , "Qualm" , "Sharp pang" , "Slight pain (of conscience?)" , "Sudden stab of pain" .)