Almost certain to block acting ruler re-emerging (9)
I believe the answer is:
resurgent
'almost certain to block acting ruler re-emerging' is the definition.
I can't tell whether this definition defines the answer.
'almost certain to block acting ruler' is the wordplay.
'almost' means to remove the last letter (almost the whole word is kept).
'certain' becomes 'sure' (synonyms).
'to block' means one lot of letters goes inside another (block can mean to plug a gap).
'acting ruler' becomes 'regent' (I've seen this before).
'sure' with its final letter removed is 'sur'.
'sur' put within 'regent' is 'RESURGENT'.
Can you help me to learn more?
(Other definitions for resurgent that I've seen before include "reborn" , "Reviving in popularity" , "given new life" , "Reviving after period of inactivity" , "making comeback" .)