Withdraw money from party, concealing security number in it (3,4)
I believe the answer is:
dip into
'withdraw money' is the definition.
'dip into' can be an answer for 'withdraw' (dipping into is a kind of withdrawing). I am unsure of the 'money' bit.
'party concealing security number in it' is the wordplay.
'party' becomes 'do' (do is a kind of party).
'concealing' indicates putting letters inside.
'security number' becomes 'pin' (a PIN number - personal identification number).
'in' means one lot of letters goes inside another.
'pin' put within 'it' is 'ipint'.
'do' going around 'ipint' is 'DIP INTO'.
'from' is the link.
Can you help me to learn more?
(Other definitions for dip into that I've seen before include "Sample" , "Take cursory interest in" , "Make use of (one's financial resources)" , "look at briefly" , "Partake of, not finishing" .)