Trace substance in pipe (10)
I believe the answer is:
smattering
'trace' is the definition.
(thesaurus)
'substance in pipe' is the wordplay.
'substance' becomes 'matter' (synonyms).
'in' indicates putting letters inside.
'pipe' becomes 'sing' (I've seen this before).
'matter' placed inside 'sing' is 'SMATTERING'.
(Other definitions for smattering that I've seen before include "Dash" , "little knowledge" , "Taste" , "superficial knowledge" , "Tiny amount (of knowledge)" .)