Decide to join switch components in metal work (3,2)
I believe the answer is:
opt in
'decide to join' is the definition.
(I've seen this in another clue)
'switch components in metal work' is the wordplay.
I cannot really see how this works, but
'in' is within the answer.
'metal' could be 'pt' (Pt is an example) and 'pt' is present in the answer.
A single letter 'o' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for opt in that I've seen before include "Choose to participate" , "Choose to take part" , "be involved voluntarily" , "Choose to be included" , "Join voluntarily" .)