Beast that insiders filled with desire (5)
I believe the answer is:
hyena
'beast' is the definition.
(I've seen this before)
'that insiders filled with desire' is the wordplay.
'insiders' means to look at the middle letters.
'filled with' indicates putting letters inside.
'desire' becomes 'yen' (yen can mean a longing or desire).
The central letters of 'that' are 'ha'.
'ha' placed around 'yen' is 'HYENA'.
(Other definitions for hyena that I've seen before include "he's a laugh" , "Dog-like carrion-feeding mammal" , "Carrion-feeding carnivore" , "Wolf-like animal with cry like laughter" , "Afr. doglike carnivore" .)