Transport leader playing on the Underground, perhaps? (7)
I believe the answer is:
busking
'playing on the underground perhaps?' is the definition.
I can't tell whether this defines the answer.
'transport leader' is the wordplay.
'transport' becomes 'bus' (bus is a kind of transport**).
'leader' becomes 'king' (King is an example).
'bus'+'king'='BUSKING'
Can you help me to learn more?
(Other definitions for busking that I've seen before include "providing entertainment for commuters?" , "Playing street music" , "street diversion" , "performing for donations" , "Performing in the street for money" .)