Course of electrotherapy probably surpasses other medication initially (5)
I believe the answer is:
epsom
'course' is the definition.
(I've seen this before)
'electrotherapy probably surpasses other medication initially' is the wordplay.
'initially' suggests taking the first letters.
The first letters of 'electrotherapy probably surpasses other medication' is 'EPSOM'.
'of' acts as a link.
(Other definitions for epsom that I've seen before include "Poems about the race-course" , "can have horses" , "Derby town" , "Poems about English racing venue" , "Mopes around in English horse-racing venue" .)