Men lose it, playing rock (9)
I believe the answer is:
limestone
'rock' is the definition.
(limestone is a kind of rock)
'men lose it playing' is the wordplay.
'playing' is an anagram indicator.
'men'+'lose'+'it'='menloseit'
'menloseit' anagrammed gives 'LIMESTONE'.
(Other definitions for limestone that I've seen before include "Sedimentary rock consisting mainly of calcium" , "building material" , "Hard calcium rock" , "Caves in here perhaps" , "Tie lemons up in sedimentary rock" .)