Extremely soporific stroll or mad rush (8)
I believe the answer is:
scramble
'mad rush' is the definition.
(I've seen this in another clue)
'extremely soporific stroll' is the wordplay.
'extremely' suggests removing the centre (only the extremes of the word are used).
'stroll' becomes 'ramble' (synonyms).
'soporific' with its middle removed is 'sc'.
'sc'+'ramble'='SCRAMBLE'
'or' is the link.
(Other definitions for scramble that I've seen before include "Disordered mixture" , "Take off immediately" , "Make one's way with disorderly haste" , "motorsport event" , "render unintelligible ..." .)