Fish on bikie's back? (13)
I believe the answer is:
leatherjacket
'fish' is the definition.
(leatherjacket is a kind of fish)
'on bikie's back?' is the wordplay.
I cannot quite understand how this works, but
'on' could be 'at' (I've seen this in other clues) and 'at' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for leatherjacket that I've seen before include "Cranefly grub" , "Lava of the crane-fly" , "Hold close" , "Garden pest - crane fly larva" , "Cranefly larva" .)