Staff member gets locked up with resistance (7)

I believe the answer is:

insider

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'staff member' is the definition.
'insider' can be an answer for 'member' (member of a group). I'm unsure of the 'staff' bit.

'locked up with resistance' is the wordplay.
'locked up' becomes 'inside' (I've seen this before).
'with' says to put letters next to each other.
'resistance' becomes 'r' (electronics abbreviation).
'inside'+'r'='INSIDER'

'gets' acts as a link.

Can you help me to learn more?

(Other definitions for insider that I've seen before include "I may know secrets" , "Dire sin (anag)" , "One of us" , "One with privileged information" , "Illegal sort of dealing" .)

I've seen this clue in The Daily Express.

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