Cap broken mescal bottles in which the spirit leaks out (9)
I believe the answer is:
ectoplasm
'in which the spirit leaks out' is the definition.
(spiritual fluid supposedly produced by mediums)
'cap broken mescal bottles' is the wordplay.
'cap' becomes 'top' ('top' can be a synonym of 'cap').
'broken' indicates anagramming the letters.
'bottles' indicates putting letters inside ('bottle' can mean to contain).
'mescal' with letters rearranged gives 'eclasm'.
'top' placed inside 'eclasm' is 'ECTOPLASM'.
(Other definitions for ectoplasm that I've seen before include "Supposed the matter" , "Supposed emanation from medium" , "Substance given off during seance" , "Material of manifested spirits" , "Substance supposedly emanating from the body of a medium during trances" .)