Second to be arrested by base tyrant (6)
I believe the answer is:
despot
'tyrant' is the definition.
(I know that tyrant can be written as despot)
'second to be arrested by base' is the wordplay.
I cannot really see how this works, but
'second' could be 's' (common abbreviation) and 's' is found in the answer.
'base' could be 'depot' (I've seen this before) and 'depot' is present in the leftover letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for despot that I've seen before include "who treats others badly?" , "Arbitrary ruler" , "has first of shocks in store" , "Cruel and oppressive dictator" , "Cruel absolute ruler" .)