One stands to play rock (9)
I believe the answer is:
sandstone
'rock' is the definition.
(I know that sandstone is a type of sedimentary rock)
'one stands to play' is the wordplay.
'to play' indicates an anagram.
'one'+'stands'='onestands'
'onestands' is an anagram of 'SANDSTONE'.
(Other definitions for sandstone that I've seen before include "Rock containing quartz grains" , "Type of sedimentary rock" , "Such building material" , "Among the best of building materials" .)