Tramp needs first ring only in cooker top (3)
I believe the answer is:
'cooker top' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for hob that I've seen before include "Small goblin" , "Top of stove" , "hot spot" , "Hot-plate" , "Top of one of 8 down" .)