Method of transport making one complain persistently (4)
I believe the answer is:
rail
'method of transport' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for rail that I've seen before include "Track - complain - bird" , "method of transport" , "Scold, berate" , "Bar of rolled steel" , "Barrier around lair" .)