Roundhead leader Royal extremists will overcome somehow (6,8)
I believe the answer is:
oliver cromwell
'roundhead leader' is the definition.
'Oliver Cromwell' can be an answer for 'leader' (Oliver Cromwell is an example). I am not certain of the 'roundhead' bit.
'royal extremists will overcome somehow' is the wordplay.
'extremists' says to hollow out the word (remove centre letters) (letters on the extreme ends of the word).
'somehow' indicates anagramming the letters.
'royal' with its middle removed is 'rl'.
'rl'+'will'+'overcome'='rlwillovercome'
'rlwillovercome' anagrammed gives 'OLIVER CROMWELL'.
Can you help me to learn more?
(Other definitions for oliver cromwell that I've seen before include "General" , "King's enemy" , "English Civil War leader" , "Statesman" .)