Newton, under tree, catches Herbert going off seniors at Trinity? (5,8)
I believe the answer is:
elder brethren
'seniors at trinity?' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'newton under tree catches herbert going off' is the wordplay.
'newton' becomes 'N' (symbol for the scientific unit of force).
'under' is a charade indicator (letters next to each other) (below, in a down clue).
'tree' becomes 'elder' (elder is a kind of tree).
'catches' indicates putting letters inside.
'going off' indicates anagramming the letters (letters go or move around).
'n' put after 'elder' is 'eldern'.
'herbert' is an anagram of 'brethre'.
'eldern' enclosing 'brethre' is 'ELDER BRETHREN'.
Can you help me to learn more?
(Other definitions for elder brethren that I've seen before include "Charitable governors" , "Governing members of the Corporation of Trinity House" .)