As worn by a master crook initially? (3)
I believe the answer is:
mac
'as' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'worn by a master crook initially?' is the wordplay.
'worn by' indicates putting letters inside.
'initially?' indicates taking the first letters (I've seen 'initially' mean this).
The first letters of 'master crook' is 'mc'.
'a' put into 'mc' is 'MAC'.
Can you help me to learn more?
(Other definitions for mac that I've seen before include "one used in shower?" , "Coat - computer" , "Waterproof raincoat, in short" , "Overcoat" , "A Gaelic son, often in name" .)