Brilliance in shrewdly using a key part (6)
I believe the answer is:
genius
'brilliance' is the definition.
(synonyms)
'using a key part' is the wordplay.
'a key' becomes 'E' (a musical key).
'part' indicates an anagram (I've seen 'parts of' mean this).
'using'+'e'='usinge'
'usinge' is an anagram of 'GENIUS'.
'in shrewdly' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for genius that I've seen before include "Guiding spirit" , "Extraordinarily intelligent person" , "Brilliance" , "Prodigy" , "Person with exceptional abitity" .)