A big bolt replaced by ring that cannot be done without (9)
I believe the answer is:
obbligato
'cannot be done without' is the definition.
I can't tell whether this definition defines the answer.
'a big bolt replaced by ring' is the wordplay.
'replaced' indicates anagramming the letters.
'by' means one lot of letters go next to another.
'ring' becomes 'O' (O is the shape of a ring).
'a'+'big'+'bolt'='abigbolt'
'abigbolt' is an anagram of 'obbligat'.
'obbligat'+'o'='OBBLIGATO'
'that' acts as a link.
Can you help me to learn more?
(Other definitions for obbligato that I've seen before include "Musical accompaniment" , "Has to be done" , "a must for the player" , "Instrumental part integral to a piece of music - I go to blab (anag)" , "having part to play always" .)