Desire to bring a customer to the best conclusion (5)
I believe the answer is:
covet
'desire' is the definition.
(I've seen this before)
'a customer to the best conclusion' is the wordplay.
'a customer' becomes 'cove' (I can't justify this - if you can you should give a lot more credence to this answer).
'to' means one lot of letters go next to another.
'conclusion' says to take the final letters.
The final letter of 'best' is 't'.
'cove'+'t'='COVET'
'to bring' is the link.
Can you help me to learn more?
(Other definitions for covet that I've seen before include "Wish for something" , "Crave something belonging to someone else" , "Jealously desire" , "Envy" , "Be envious" .)