A rascal between the aisles they say (5)
I believe the answer is:
knave
'a rascal' is the definition.
(I know that rascal can be written as knave)
'between the aisles they say' is the wordplay.
'between the aisles' becomes 'nave' (nave is a part of a church).
'they say' indicates a 'sounds like' (homophone) clue.
'nave' is a homophone of 'KNAVE'.
(Other definitions for knave that I've seen before include "Jack - scoundrel" , "cheat of old" , "A swindler" , "[COURT CARD] , maybe" , "Yet he may be a diamond" .)