Give new order to back line of products (9)
I believe the answer is:
rearrange
'line of products' is the definition.
The answer and definition can be both related to change as well as being verbs in their base form.
Perhaps you can see an association between them that I can't see?
'give new order to back' is the wordplay.
I cannot really see how this works, but
'give' could be 'range' (ranging is a kind of giving) and 'range' is present in the answer.
'back' could be 'rear' (something's rear is its back) and 'rear' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for rearrange that I've seen before include "Rear anger (anag.)" , "Change the position(s) of" , "Make an anagram of" , "Move round" , "Organise another way" .)