Member following a Labour leader creates dismay (5)
I believe the answer is:
alarm
'dismay' is the definition.
('alarm' can be a synonym of 'dismay')
'member following a labour leader' is the wordplay.
'member' becomes 'arm' (arm is a kind of member).
'following' means one lot of letters go next to another.
'leader' says to take the initial letters.
The initial letter of 'labour' is 'l'.
'a'+'l'='al'
'arm' put after 'al' is 'ALARM'.
'creates' is the link.
(Other definitions for alarm that I've seen before include "Feeling of fear" , "Alternative to reveille" , "Strike fear" , "Mild panic" , "Daunt" .)