Red felt tip's missing top, finally running out (7)
I believe the answer is:
leftist
'red' is the definition.
(I've seen this before)
'tip's missing top finally running out' is the wordplay.
'tip' becomes 'list'.
'missing top' means to remove the first letter.
'finally' says to put letters next to each other.
'running out' becomes 'left' (I am not sure about this - if you are sure you should believe this answer much more).
'list' with its first letter taken away is 'ist'.
'ist' put after 'left' is 'LEFTIST'.
'felt' is the link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for leftist that I've seen before include "Radical politician" , "Socialist supporter" , "Supporter of socialism" , "Red" , "Labourite" .)