Struggles with mysterious tablets (7)
I believe the answer is:
battles
'struggles' is the definition.
('battle' can be a synonym of 'struggle')
'mysterious tablets' is the wordplay.
'mysterious' indicates anagramming the letters.
'tablets' with letters rearranged gives 'BATTLES'.
'with' acts as a link.
(Other definitions for battles that I've seen before include "Military engagements" , "Fights, conflicts" , "Lengthy conflicts" , "Campaigns" , "Military set pieces" .)