Going to great lengths at either end (7)
I believe the answer is:
extreme
This might be a double definition.
'going to great lengths' is the first definition.
(I've seen this before)
'either end' is the second definition.
'extreme' can be an answer for 'end' (I've seen this before). I am unsure of the 'either' bit.
'at' acts as a link.
Can you help me to learn more?
(Other definitions for extreme that I've seen before include "lacking moderation" , "end" , "Very great; exceptional" , "sheer" , "Ultimate" .)