Prison sentence given to youth leader supplying elastic (8)
I believe the answer is:
stretchy
'elastic' is the definition.
(similar in meaning)
'prison sentence given to youth leader' is the wordplay.
'prison sentence' becomes 'stretch' (I've seen this in another clue).
'given to' is a charade indicator (letters next to each other).
'youth leader' becomes 'y' (I've seen this in other clues).
'stretch'+'y'='STRETCHY'
'supplying' is the link.
(Other definitions for stretchy that I've seen before include "Flexible" , "Elastic" , "Of variable length, perhaps" .)