Children primarily linger outside small arcade (8)
I believe the answer is:
cloister
'arcade' is the definition.
(I know that cloister is a type of arcade)
'children primarily linger outside small' is the wordplay.
'primarily' suggests taking the first letters.
'linger' becomes 'loiter' (synonyms).
'outside' means one lot of letters goes inside another (some letters go outside others).
'small' becomes 's' (abbreviation - e.g. clothes size).
The initial letter of 'children' is 'c'.
'loiter' placed around 's' is 'loister'.
'c'+'loister'='CLOISTER'
(Other definitions for cloister that I've seen before include "Covered walk by cathedral etc" , "Monastic life" , "Costlier in monastery" , "Covered walk round quadrangle" , "Covered passage round cathedral courtyard" .)