Expert note about being solvent (7)
I believe the answer is:
acetone
'being solvent' is the definition.
(I've seen this before)
'expert note about' is the wordplay.
'expert' becomes 'ace' (ace can informally mean very good).
'about' is an anagram indicator.
'note' is an anagram of 'tone'.
'ace'+'tone'='ACETONE'
(Other definitions for acetone that I've seen before include "it dissolves" , "Paint thinner" , "chemical is the solution" , "Remover of nail polish" , "Inflammable liquid" .)