Steal post, disposing of first letter (4)
I believe the answer is:
take
'steal' is the definition.
(to steal is to take without permission)
'post disposing of first letter' is the wordplay.
'post' says to put letters next to each other (post- can mean after).
'disposing of first' becomes 'tak' (I can't explain this - if you can you should give a lot more credence to this answer).
'letter' becomes 'e'.
'tak' put next to 'e' is 'TAKE'.
Can you help me to learn more?
(Other definitions for take that I've seen before include "catch" , "Accept, receive" , "Money received" , "Consume (drugs)" , "Snatch" .)