LETTER BANK XXX

In a letter bank, the letters of one word are used - and repeated as necessary - to spell a longer word or phrase. No other letters are allowed. For example, IMPS is a letter bank for MISSISSIPPI.

In the flat below, the keyword SHORT represents the letter bank.

My problem is that I don't know much.
I say "I'm new" and that's my crutch.
So that's the way it is for me;
The LONG of being a SHORT you see.

HINT:
SHORT stands for a word that means someone who is new at something.

Answer:

SHORT = NOVICE
LONG = INCONVENIENCE

Credit:
The Enigma
NPL Magazine
November, 2019
ANDREAS