Physicist — one going on and on endlessly about hydrogen (4)
I believe the answer is:
bohr
'physicist' is the definition.
(I've seen this before)
'one going on and on endlessly about hydrogen' is the wordplay.
'one going on and on' becomes 'wordy' (I've seen this in another clue).
'endlessly' says to take the centre (the ends of the words are removed).
'about' means one lot of letters go next to another.
'hydrogen' becomes 'boh' (I can't justify this - if you can you should believe this answer much more).
The central letter of 'wordy' is 'r'.
'r' put after 'boh' is 'BOHR'.
Can you help me to learn more?
(Other definitions for bohr that I've seen before include "Danish Nobel-winning physicist (father or son)" , "scientist" , "Niels -, Danish Nobel physicist" .)