The most common and most likely answer to this crossword clue is the 8 plus 6 letter word OPPOSITE NUMBER
I've seen this crossword clue in The Daily Telegraph
O
P
P
O
S
I
T
E
N
U
M
B
E
R
More clues leading to the result OPPOSITE NUMBER
- , 16 Partner in, Mrs out: Bo Peep going out
- He does my job for rivals over the road with less feeling
- Counterpart of old Poe’s ‘Pit’, revised edition
- Person in similar position crazily bit me on purpose
- Counterpart to Pope is converted, supported by cardinal
- Work poet is developing with song for a counterpart
- E.g. ten to four on watch for counterpart
- Counterpart to pope is afflicted with senseless hesitation
- Person with similar job in house across the street?
- Counterpart stupidly bit me on purpose
Buddy explains!

The straight part
We know that "a counterpart" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a counterpart = opposite number.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.