Fit into an epic tussle (5)
I believe the answer is:
ictus
'fit' is the definition.
(thesaurus)
'into an epic tussle' is the wordplay.
'into' indicates a hidden word.
'ICTUS' can be found hidden inside 'epic tussle'.
(Other definitions for ictus that I've seen before include "Metrical stress" , "strokes" , "Seizure" , "Sudden attack" , ""fit"" .)