English monarch dismissing first King's Mathematician (5)
I believe the answer is:
euler
'mathematician' is the definition.
(I've seen this before)
'english monarch dismissing first king's' is the wordplay.
'english monarch' becomes 'eu' (I can't justify this - if you can you should believe this answer much more).
'dismissing' suggests deleting specific letters.
'first' becomes 'a' (first letter of the alphabet).
'king' becomes 'lear' (King Lear).
'lear' with 'a' taken away is 'ler'.
'eu'+'ler'='EULER'
Can you help me to learn more?
(Other definitions for euler that I've seen before include "Swiss scientist" , "calculating foreigner" , "Eighteen-hole game" , "18th-century Swiss mathematician and physicist" , "Leonhard --, C18 Swiss mathematician" .)