The most common and most likely answer to this crossword clue is the 7 letter word LENDING
I've seen this crossword clue in The Sunday Telegraph
L
E
N
D
I
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G
More clues leading to the result LENDING
Buddy explains!

The straight part
We know that "Advancing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case advancing = lending.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does LENDING mean?
LENDING verb- To allow to be used by someone temporarily, on condition that it or its equivalent will be returned.
- To make a loan.
- To be suitable or applicable, to fit.
- To afford; to grant or furnish in general.
- To borrow.
- The action of, or an instance of the action of the verb to lend.
- That lends.