Queen Victoria's beginning to interrupt all her children, quelling excitement? (7)

'quelling excitement?' is the definition.
(a nervine medicine calms nerves)

'queen victoria's beginning to interrupt all' is the wordplay.
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'beginning to' suggests taking the first letters.
'interrupt' means one lot of letters goes inside another.
'all' becomes 'nine' (I can't explain this - if you can you should believe this answer much more).
The initial letter of 'victoria' is 'v'.
'er'+'v'='erv'
'erv' going inside 'nine' is 'NERVINE'.

'her children' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.