Folk rock boat close to shore: 50 aboard (7)
I believe the answer is:
skiffle
'folk' is the definition.
(I know that skiffle is a type of contemporary folk music)
'boat close to shore 50 aboard' is the wordplay.
'boat' becomes 'skiff' (skiff is a kind of boat).
'close to' indicates one should take the final letters (the close of something is the end).
'f0' becomes 'l' (Roman numeral).
'aboard' indicates putting letters inside.
The last letter of 'shore' is 'e'.
'skiff'+'e'='skiffe'
'skiffe' enclosing 'l' is 'SKIFFLE'.
'rock' is the link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for skiffle that I've seen before include "Music style using, eg, washboards" , "1950s popular music genre" , "Style of music from the 1950s" , "folk rock, Fifties-style" , "Style of music popularised Lonnie Donegan" .)