Very happy about copper rod for electrical component (7,6)
I believe the answer is:
mercury switch
'electrical component' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.
'very happy about copper rod' is the wordplay.
'very happy about copper' becomes 'mercury' (I can't justify this - if you can you should believe this answer much more).
'rod' becomes 'switch' (I've seen this before).
'mercury'+'switch'='MERCURY SWITCH'
'for' acts as a link.
Can you help me to learn more?
(Another definition for mercury switch that I've seen is " one's tipped on and off".)