Smart, like a frock? (6)
I believe the answer is:
'smart' is the definition.
(I've seen this in another clue)
'like a frock?' is the wordplay.
I cannot quite see how this works, but
'like' could be 'y' (similar in meaning) and 'y' is located in the answer.
'frock?' could be 'dress' (frocking is a kind of dressing) and 'dress' is found in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for dressy that I've seen before include "Liking to wear fancy or formal clothes" , "Elaborate" , "(Of clothes) smart, formal" , "Smartly clothed" , "'Stylish, smart (6)'" .)