Physicist’s unusually strong backing graduate receives (8)
I believe the answer is:
angstrom
'physicist's' is the definition.
(I've seen this before)
'unusually strong backing graduate receives' is the wordplay.
'unusually' indicates an anagram.
'backing' is a reversal indicator.
'graduate' becomes 'ma' (abbreviation for Master of Arts).
'receives' indicates putting letters inside.
'ma' reversed gives 'am'.
'strong' anagrammed gives 'ngstro'.
'ngstro' placed within 'am' is 'ANGSTROM'.
(Other definitions for angstrom that I've seen before include "virtually no distance!" , "Rabbit" , "A small measure" , "Tiny unit of length used in Physics" , "Wavelength produced" .)