Giant periodical with dogs between the covers (5)
I believe the answer is:
magog
'giant' is the definition.
(I've seen this before)
'periodical with dogs between the covers' is the wordplay.
I cannot quite see how this works, but
'periodical' could be 'mag' (short for magazine) and 'mag' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for magog that I've seen before include "Gog and -, City of London guardian giants" , "Gog's companion" , "Biblical king" , "Last of two old giants" , "old giant" .)