Part of spur moved lower (5)
I believe the answer is:
rowel
'part of spur' is the definition.
(part of a spur used in horse-riding)
'moved lower' is the wordplay.
'moved' is an anagram indicator.
'lower' anagrammed gives 'ROWEL'.
(Other definitions for rowel that I've seen before include "Part of a spur" , "piece on Spurs" , "Spur's spiked disc" , "Spur's spiked wheel" , "Spur spike" .)