The most common and most likely answer to this crossword clue is the 10 letter word UNILATERAL
I've seen this crossword clue in Independent
U
N
I
L
A
T
E
R
A
L
More clues leading to the result UNILATERAL
- School now, then this? A learner's acting alone
- One-sided police lie naturally, but not extremely libellously
- College lecturer after a tense period left being one-sided
- Perhaps Berkeley’s after a Liberal from one side
- One-sided varsity man seen around subsequently
- One-sided lie, natural misbehaviour
- One-sided version of a Latin rule
- Nothing worried visiting Russian banker in involving just one party
- Redeveloped area until left by one side
Buddy explains!

The straight part
We know that "One-sided" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one-sided = unilateral.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 UNILATERAL mean?
UNILATERAL adjective- Done by one side only.
- Affecting only one side of the body.
- Binding or affecting one party only.