Spinning out a letter to the monarch (5)
I believe the answer is:
eking
'spinning out' is the definition.
The definition suggests a verb in its base form which matches the answer.
'a letter to the monarch' is the wordplay.
'a letter' becomes 'e'.
'to the monarch' becomes 'king' (king is a kind of monarch).
'e'+'king'='EKING'
Can you help me to learn more?
(Other definitions for eking that I've seen before include "Making last longer by careful use" , "Managing to make (a living)" , "spinning?" , "... stretching" , "Squeezing (out)" .)