Regarding Melbourne's first cricket ground dismissal (7)
I believe the answer is:
removal
'dismissal' is the definition.
(I know that removal is a type of dismissal)
'regarding melbourne's first cricket ground' is the wordplay.
'regarding' becomes 're' (re can mean regarding, concerning).
'melbourne's first' becomes 'm' (1st letter of 'melbourne').
'cricket ground' becomes 'oval' (London cricket ground).
're'+'m'+'oval'='REMOVAL'
(Other definitions for removal that I've seen before include "Transferral" , "Deletion" , "purge" , "Change of location" , "Taking (of thing) away" .)