Planet-beater, head to tail (5)
I believe the answer is:
earth
'planet' is the definition.
(Earth is an example)
'head to tail' is the wordplay.
'head' becomes 'ear' (I have seen 'Head of corn' mean 'ear' so perhaps 'head' could also mean 'ear').
'to tail' becomes 'th' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'ear'+'th'='EARTH'
'beater' acts as a link.
This may not be right. It may be part of another bit of the clue.
(Other definitions for earth that I've seen before include "our present abode" , "Land" , "dirt" , "Make electrics safe" , "Connection between an electrical device and conductor" .)