Stress needing Junior to queue (9)
I believe the answer is:
underline
'stress' is the definition.
(underlining is a kind of stressing)
'junior to queue' is the wordplay.
'junior' becomes 'under' (I've seen this in other clues).
'to queue' becomes 'line' (I've seen this before).
'under'+'line'='UNDERLINE'
'needing' is the link.
(Other definitions for underline that I've seen before include "Method of showing emphasis in writing" , "Emphasise, stress importance" , "Emphasize, stress importance" , "Reinforce" , "Form of emphasis in writing" .)