Item in magazine showing extraction of power from proton, say (7)
I believe the answer is:
article
'item in magazine' is the definition.
(article in a magazine)
'power from proton say' is the wordplay.
'power' becomes 'p'.
'from' suggests deleting specific letters.
'proton say' becomes 'particle' (proton is a type of subatomic particle).
'particle' with 'p' taken away is 'ARTICLE'.
'showing extraction of' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
(Other definitions for article that I've seen before include "You might say one" , "'The', definitely" , "See 10" , "Possibly the" , "something" .)