Copper spends time and energy to appear endearing (4)
I believe the answer is:
cute
'endearing' is the definition.
(I've seen this before)
'copper spends time and energy' is the wordplay.
'copper' becomes 'cu' (chemical symbol).
'spends' indicates an anagram (I've seen 'spent' mean this).
'time' becomes 't' (abbreviation).
'and' is a charade indicator (letters next to each other).
'energy' becomes 'e' (physics symbol as in E=mcu).
't' put after 'e' is 'et'.
'et' with letters rearranged gives 'te'.
'cu'+'te'='CUTE'
'to appear' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for cute that I've seen before include "Clever - attractive" , "Quaintly attractive" , "Astute - lovely" , "Attractive and quaint (4" , "Endearingly pretty" .)