That of a square, always? (4)
I believe the answer is:
area
'that of a square always?' is the definition.
I can't judge whether this definition defines the answer.
'of a square always?' is the wordplay.
'of' says the answer is hidden in the clue.
'AREA' is hidden in the letters of 'square always'.
Can you help me to learn more?
(Other definitions for area that I've seen before include "District; plot" , "Part of a building, city etc" , "topic" , "Geographical region" , "environs" .)