Caught idle round small arcade (8)
I believe the answer is:
cloister
'arcade' is the definition.
(I know that cloister is a type of arcade)
'caught idle round small' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'idle' becomes 'loiter' (I've seen this in another clue).
'round' is an insertion indicator.
'small' becomes 's' (abbreviation - e.g. clothes size).
'loiter' going around 's' is 'loister'.
'c'+'loister'='CLOISTER'
(Other definitions for cloister that I've seen before include "Covered monastic walkway" , "put within walls" , "Covered walk in religious institution" , "Covered walk in monastery or convent" , "Costlier in monastery" .)