The partridge's spine (5)
I believe the answer is:
ridge
'spine' is the definition.
(I've seen this in another clue)
'the partridge's' is the wordplay.
'RIDGE' is hidden within the letters.
But, I am uncertain how this is indicated.
Can you help me to learn more?
(Other definitions for ridge that I've seen before include "there's a lot of pressure in it" , "Top line of roof" , "Narrow raised band on a surface" , "Narrow hill-range" , "Crest - reef" .)