Monarch by pit sees white weasel (6)
I believe the answer is:
ermine
'white weasel' is the definition.
'ermine' can be an answer for 'weasel' (ermine is a kind of weasel). I am unsure of the 'white' bit.
'monarch by pit' is the wordplay.
'monarch' becomes 'ER' (abbreviation for Elizabeth Regina, British Queen).
'by' says to put letters next to each other.
'pit' becomes 'mine' (mining pit).
'er'+'mine'='ERMINE'
'sees' acts as a link.
Can you help me to learn more?
(Other definitions for ermine that I've seen before include "Warm white covering" , "Animal with brown fur that turns white in winter" , "garb for nobility" , "special trimmings" , "White fur associated with judges" .)