Youth leader's clanger, shielding internee at port (5-6)
I believe the answer is:
baden-powell
'youth leader's' is the definition.
(I've seen this before)
'clanger shielding internee at port' is the wordplay.
'clanger' becomes 'bell' (something which clangs).
'shielding' means one lot of letters goes inside another.
'internee' becomes 'POW' (prisoner of war).
'at' says to put letters next to each other (I've seen this in other clues).
'port' becomes 'aden' (port in Yemen).
'pow' put after 'aden' is 'adenpow'.
'bell' going around 'adenpow' is 'BADEN-POWELL'.
(Other definitions for baden-powell that I've seen before include "Scout founder" , "Scouting founder" , "Scouts founder" , "Author of Scouting for Boys" .)