Support but don't allow to proceed (4,2)
I believe the answer is:
hold up
'support' is the definition.
(I know that support can be written as hold up)
'don't allow to proceed' is the wordplay.
'don't allow' becomes 'up' (I can't explain this - if you can you should believe this answer much more).
'to' says to put letters next to each other (I've seen this in other clues).
'proceed' becomes 'hold' (holding is a kind of proceeding).
'up' put after 'hold' is 'HOLD-UP'.
'but' acts as a link.
Can you help me to learn more?
(Other definitions for hold up that I've seen before include "Hitch" , "Support by arms - threaten by arms" , "Survive" , "Delay" , "robbery" .)