The most common and most likely answer to this crossword clue is the 4 plus 3 plus 6 letter word BAIT AND SWITCH
B
A
I
T
A
N
D
S
W
I
T
C
H
Buddy explains!
The straight part
We know that "unscrupulous sales tactic" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unscrupulous sales tactic = bait and switch.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.