Lie initially told every second by party supporter (4,5)
I believe the answer is:
tall story
'lie' is the definition.
(I've seen this before)
'initially told every second by party supporter' is the wordplay.
'initially' says to take the initial letters.
'every' becomes 'all' (similar in meaning).
'second by party supporter' becomes 'story' (I am not sure about this - if you are sure you should believe this answer much more).
The initial letter of 'told' is 't'.
't'+'all'+'story'='TALL STORY'
Can you help me to learn more?
(Other definitions for tall story that I've seen before include "Remarkable tale" , "unreliable account" , "romance?" , "Exaggerated tale" , "Incredible account" .)