Sneak around in novel disguise (5)
I believe the answer is:
sidle
'sneak' is the definition.
(thesaurus)
'around in novel disguise' is the wordplay.
'around' shows that the letters should be reversed in order.
'in' says the answer is hidden in the clue.
'eldis' can be found hidden inside 'novel disguise'.
'eldis' written backwards gives 'SIDLE'.
(Other definitions for sidle that I've seen before include "Walk sideways like crab" , "Move along sideways" , "steal" , "Walk sideways in furtive manner" , "Isled (anag.)" .)