Nail tonal difference (5)
I believe the answer is:
talon
'nail' is the definition.
(thesaurus)
'tonal difference' is the wordplay.
'difference' is an anagram indicator.
'tonal' is an anagram of 'TALON'.
(Other definitions for talon that I've seen before include "one that grips" , "The stock" , "part to make savage cuts" , "Claw; undealt cards" , "Eagle claw" .)