Pinch sodium and boron (3)
I believe the answer is:
nab
'pinch' is the definition.
(I've seen this before)
'sodium and boron' is the wordplay.
'sodium' becomes 'NA' (Na is the chemical symbol for sodium).
'and' says to put letters next to each other.
'boron' becomes 'B' (synonyms).
'na'+'b'='NAB'
(Other definitions for nab that I've seen before include "Catch (thief) (colloq.)" , "Apprehend" , "Catch (a felon)" , "Capture, catch" , "Take" .)