Beast could be intimate without resistance (5)
I believe the answer is:
fiend
'beast' is the definition.
(thesaurus)
'intimate without resistance' is the wordplay.
'intimate' becomes 'friend' (intimate can mean a friend).
'without' indicates named letters should be taken away.
'resistance' becomes 'r' (electronics abbreviation).
'friend' with 'r' taken out is 'FIEND'.
'could be' acts as a link.
(Other definitions for fiend that I've seen before include "monster" , "Devil" , "Demon, ogre" , "Demon; cruel person" , "Evil spirit, demon" .)