Insufficient supplies are a fright, Charlie admitted (6) (6)
I believe the answer is:
scarce
'insufficient' is the definition.
(similar in meaning)
'charlie admitted 6' is the wordplay.
'charlie' becomes 'C' (phonetic alphabet: alpha, bravo, charlie etc.).
'admitted' indicates putting letters inside (inserted letters get admitted).
'6' becomes 'scare' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'c' going into 'scare' is 'SCARCE'.
'supplies are a fright' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for scarce that I've seen before include "Falling short of demand" , "Hardly" , "Common? Definitely not" , "Not enough to satisfy demand" , "Not often found" .)