Break under 50 Ronnie's last - it's unexpected (9)
I believe the answer is:
interlude
'break' is the definition.
(thesaurus)
'under 50 ronnie's last it's unexpected' is the wordplay.
I cannot quite understand how this works, but
'50' could be 'l' (Roman numeral) and 'l' is found in the answer.
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found within the answer.
an anagram of 'under' is 'nerud' which is within the remaining letters.
The remaining letters 'ie' 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).
Can you help me to learn more?
(Other definitions for interlude that I've seen before include "Pause" , "Intermission, break" , "Hiatus" , "Intervening period" , "Eli turned (anag.)" .)