Ruler is powerful when swallowed (9)
I believe the answer is:
potentate
'ruler' is the definition.
(I know that potentate is a type of ruler)
'powerful when swallowed' is the wordplay.
I cannot quite understand how this works, but
'powerful' could be 'potent' (associated in meaning) and 'potent' is found in the answer.
'when' could be 'e' (I've seen this in other clues) and 'e' is present in the answer.
The remaining letters 'at' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'is' acts as a link.
Can you help me to learn more?
(Other definitions for potentate that I've seen before include "authority" , "A monarch or ruler" , "Powerful autocratic ruler" , "Mogul" .)