Where it could be nice for mum to just sit and watch (6)
I believe the answer is:
cinema
'where it could' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'nice for mum to just sit and watch' is the wordplay.
I cannot quite see how this works, but
an anagram of 'nice' is 'cine' which is within the answer.
'mum' could be 'ma' ('ma' can be a synonym of 'mum') and 'ma' is found within the answer.
This accounts for all the letters.
This may be the basis of clue (or it may be nonsense).
'be' is the link.
Can you help me to learn more?
(Other definitions for cinema that I've seen before include "Iceman (anag)" , "Place of entertainment" , "Silver screen" , "Movie-house" , "(Building showing) films" .)