Baker perhaps next to butcher's back at one-way system (7)
I believe the answer is:
ratchet
'one-way system' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'baker perhaps next to butcher's back at' is the wordplay.
'baker perhaps' becomes 'Chet' (trumpeter Chet Baker).
'next to' says to put letters next to each other.
'back' suggests the final letters (the letter at the back).
The final letter of 'butcher' is 'r'.
'r'+'at'='rat'
'chet' after 'rat' is 'RATCHET'.
Can you help me to learn more?
(Other definitions for ratchet that I've seen before include "Device preventing backward motion" , "Mechanism with a toothed bar or wheel" , "One-way toothed wheel" , "Make steady progress" , "One-way mechanism" .)