Wise one entered stand without a hat (6)
I believe the answer is:
bowler
'a hat' is the definition.
(I know that bowler is a type of hat)
'wise one entered stand without' is the wordplay.
'wise one' becomes 'owl' (I've seen this in another clue).
'entered stand' becomes 'ber' (I am not sure about this - if you are sure you should believe this answer much more).
'without' indicates putting letters inside.
'owl' inserted into 'ber' is 'BOWLER'.
Can you help me to learn more?
(Other definitions for bowler that I've seen before include "He likes a flat green" , "Type of hat" , "One who can deliver" , "Sportsman" , "See 8" .)