Wicked criminal lady pinching sparkler diamonds (9)

I believe the answer is:

dastardly

I'm a little stuck... Click here to teach me more about this clue!

'wicked' is the definition.
Both the definition and answer are adjectives. Maybe there's an association between them I don't understand?

'criminal lady pinching sparkler diamonds' is the wordplay.
'criminal' indicates anagramming the letters.
'pinching' is an insertion indicator (taking inside).
'sparkler' becomes 'star' (I can't explain this - if you can you should believe this answer much more).
'diamonds' becomes 'd' (abbreviation in bridge say).
'lady' with letters rearranged gives 'daly'.
'star'+'d'='stard'
'daly' enclosing 'stard' is 'DASTARDLY'.

Can you help me to learn more?

(Other definitions for dastardly that I've seen before include "Despicable" , "Cruel" , "Iniquitous" , "contemptible" , "Cowardly" .)

I've seen this clue in The Independent.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.