Climb on a fish's back (5)
I believe the answer is:
scale
This clue might be a double definition.
'climb' is the first definition.
(I know that scale is a type of climb)
'fish's back' is the second definition.
The answer and definition can be both man-made objects as well as being singular nouns.
I also know that 'fish' relates to this answer.
'on a' is the link.
Can you help me to learn more?
(Other definitions for scale that I've seen before include "Alec's (anag) -- graduation" , "Climb, or series of notes in music" , "Horny plate; balance" , "Tones rising maybe" , "Deposit formed in a kettle or on teeth" .)