At the back, Charlie Lunnon held firm, tho’ was caught finally (7)
I believe the answer is:
endmost
'at the back' is the definition.
(endmost means nearest to the end)
'charlie lunnon held firm tho' was caught finally' is the wordplay.
'finally' says to take the final letters.
The last letters of 'charlie lunnon held firm tho was caught' are 'ENDMOST'.
(Other definitions for endmost that I've seen before include "Last in a row" , "extreme situation" , "final" , "Last in the line" , "Most distant" .)