Drama Niamh embodies is an obsession (5)
I believe the answer is:
mania
'an obsession' is the definition.
(I've seen this before)
'drama niamh embodies' is the wordplay.
'embodies' says the answer is hidden in the clue.
'MANIA' is hidden in the letters of 'drama niamh'.
'is' is the link.
(Other definitions for mania that I've seen before include "serious obsession" , "Mental disorder that results in excessive or violent responses" , "fixation" , "Madness - craze" , "Craze; overexcitement" .)