Group regularly books return trip (4)
I believe the answer is:
tour
'trip' is the definition.
(thesaurus)
'group regularly books return' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'books' becomes 'ot' (Old Testament).
'return' is a reversal indicator.
The alternate letters of 'group' are 'ru'.
'ru'+'ot'='ruot'
'ruot' back-to-front is 'TOUR'.
(Other definitions for tour that I've seen before include "Go on holiday or inspection journey" , "Journey to visit places of interest" , "Rout (anag.)" , "Extensive journey" , "A trip round" .)