Ms Darling did it as a royal favour (3,2,5)

'royal favour' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'ms darling did it as a' is the wordplay.
I cannot really understand how this works, but
'darling' could be 'grace' (Grace Darling saved lives after an 1838 shipwreck) and 'grace' is present in the answer.
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found within the answer.
'a' is within the answer.
This explanation may well be incorrect...

Can you help me to learn more?