He takes a hard line, the beast! (5)
I believe the answer is:
hiram
'he' is the definition.
'a hard line the beast' is the wordplay.
'a hard line' becomes 'hi' (I can't justify this - if you can you should give a lot more credence to this answer).
'the beast' becomes 'ram' (I've seen this in other clues).
'hi'+'ram'='HIRAM'
'takes' acts as a link.
Can you help me to learn more?
(Other definitions for hiram that I've seen before include "I gave Solomon materials for Temple" , "He supplied temple builders" .)