Runner goes around a Munro (4)
I believe the answer is:
saki
'munro' is the definition.
(H H Munro - writer with the pen name Saki)
'runner goes around a' is the wordplay.
'runner' becomes 'ski' (ski is a kind of runner).
'goes around' indicates putting letters inside.
'ski' enclosing 'a' is 'SAKI'.
(Other definitions for saki that I've seen before include "drink in Tokyo" , "Pseudonymous English writer" , "Scottish writer" , "Monkey; author's pen name" , "author chosen by 29" .)