Fixing a bell outside the entrance is of little importance (9)
I believe the answer is:
bagatelle
'of little importance' is the definition.
The definition suggests a singular noun which matches the answer.
'fixing a bell outside the entrance' is the wordplay.
'fixing' indicates anagramming the letters.
'outside' is an insertion indicator.
'the entrance' becomes 'gate' (I've seen this before).
'a'+'bell'='abell'
'abell' with letters rearranged gives 'balle'.
'balle' going around 'gate' is 'BAGATELLE'.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for bagatelle that I've seen before include "lovely trinket" , "no serious work" , "Trivial matter" , "Something trivial" , "trifling amount" .)