The most common and most likely answer to this crossword clue is the 8 plus 7 letter word SECURITY DEPOSIT
I've seen this crossword clue in The Daily Telegraph
S
E
C
U
R
I
T
Y
D
E
P
O
S
I
T
Buddy explains!
The straight part
We know that "Payment to landlord" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case payment to landlord = security deposit.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.