The most common and most likely answer to this crossword clue is the 13 letter word PROPORTIONATE
P
R
O
P
O
R
T
I
O
N
A
T
E
Buddy explains!

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 PROPORTIONATE mean?
PROPORTIONATE verb- To make proportionate.
- In proportion; proportional; commensurable.
- Harmonious and symmetrical.