Penny discovered Tom Jones, a Welsh singer, cycling on board boat (6)
I believe the answer is:
pedalo
'boat' is the definition.
(I know that pedalo is a type of boat)
'penny discovered tom' is the wordplay.
'penny' becomes 'pedal' (I am not sure about this - if you are sure you should believe this answer much more).
'discovered' indicates the central letters (dis-covered - outer letters removed).
The centre of 'tom' is 'o'.
'pedal'+'o'='PEDALO'
'jones a welsh singer cycling on board' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for pedalo that I've seen before include "Small foot-powered pleasure boat" , "Paddle boat" , "Foot-powered pleasure craft" , "Man-powered leisure boat" , "Foot-operated boat" .)