Courage shown by last in convoy in sound (6)
I believe the answer is:
hearty
'sound' is the definition.
(thesaurus)
'courage shown by last in convoy' is the wordplay.
'courage' becomes 'heart' (heart is a kind of courage).
'shown by' means one lot of letters go next to another.
'last in' says to take the final letters.
The last letter of 'convoy' is 'y'.
'heart'+'y'='HEARTY'
'in' is the link.
(Other definitions for hearty that I've seen before include "Vigorously warm and friendly" , "Substantial and nourishing" , "Jovial fellow" , "Enthusastic" , "shipmate?" .)