Reverse hack newspaper and make aunt massive (10)
I believe the answer is:
gargantuan
'massive' is the definition.
(synonyms)
'reverse hack newspaper and make aunt' is the wordplay.
'reverse' says the letters should be written in reverse.
'hack' becomes 'nag' (synonyms).
'newspaper' becomes 'rag' (informal term for a newspaper).
'and' is a charade indicator (letters next to each other).
'make' indicates an anagram.
'nag'+'rag'='nagrag'
'nagrag' in reverse letter order is 'gargan'.
'aunt' with letters rearranged gives 'tuan'.
'gargan'+'tuan'='GARGANTUAN'
(Other definitions for gargantuan that I've seen before include "Massive" , "Huge" , "Tremendous" , "Prodigious" , "Enormous" .)