Hunter of rhino regularly ending in prison (5)
I believe the answer is:
orion
'hunter' is the definition.
(I've seen this before)
'of rhino regularly ending in prison' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'ending in' indicates one should take the final letters.
The last letter of 'prison' is 'n'.
'of'+'rhino'='ofrhino'
The alternate letters of 'ofrhino' are 'orio'.
'orio'+'n'='ORION'
(Other definitions for orion that I've seen before include "Heavenly figure" , "Greek hunter became a constellation" , "Great hunter of Greek legend and a constellation" , "Bright constellation, named after legendary Greek hunter" , "Constellation - mythological hunter" .)