English set about interrupting public transport message (8)
I believe the answer is:
telegram
'message' is the definition.
(telegram is a kind of message)
'english set about interrupting public transport' is the wordplay.
'english' becomes 'e' (abbreviation).
'set' becomes 'gel' (I've seen this before**).
'about' is a reversal indicator.
'interrupting' is an insertion indicator.
'public transport' becomes 'tram' (I've seen this before).
'gel' reversed gives 'leg'.
'e'+'leg'='eleg'
'eleg' going within 'tram' is 'TELEGRAM'.
(Other definitions for telegram that I've seen before include "Electric message" , "Message transmitted by wire" , "Pre-1980s electronic message" , "Now obsolete communication over a wire" , "cable" .)