The most common and most likely answer to this crossword clue is the 13 letter word MINIATURISING
M
I
N
I
A
T
U
R
I
S
I
N
G
More clues leading to the result MINIATURISING
Buddy explains!

The straight part
We know that "Making small" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case making small = miniaturising.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 MINIATURISING mean?
MINIATURISING verb- To design or construct something on a miniature scale.