Personal assistant's weapon — that will get you access! (8)
I believe the answer is:
password
'that will get you access' is the definition.
(word allowing someone access to something)
'personal assistant's weapon' is the wordplay.
'personal assistant's' becomes 'PA's' (abbreviation).
'weapon' becomes 'sword' (sword is a kind of weapon).
'pas'+'sword'='PASSWORD'
(Other definitions for password that I've seen before include "one maybe stolen by 21 [HACKER]" , "Eg, open sesame" , "parole" , "keep this secret?" , "Sign to gain admittance" .)