Not enough in a sample of dust to match with (10)
I believe the answer is:
inadequate
'not enough' is the definition.
(thesaurus)
'in a sample of dust to match with' is the wordplay.
'sample of' says to take the initial letters.
'to match with' becomes 'equate'.
The initial letter of 'dust' is 'd'.
'in'+'a'+'d'+'equate'='INADEQUATE'
(Other definitions for inadequate that I've seen before include "not up to the job" , "Found wanting" , "Falling short of requirements" , "Insufficient" , "lacking" .)