The most common and most likely answer to this crossword clue is the 7 letter word THWARTS
I've seen this crossword clue in The Daily Telegraph
T
H
W
A
R
T
S
Buddy explains!
The straight part
We know that "Obstructs/rowers’ benches" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case obstructs/rowers’ benches = thwarts.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 THWARTS mean?
THWARTS noun- A seat across a boat on which a rower may sit.
- A brace, perpendicular to the keel, that helps maintain the beam of a marine vessel against external water pressure and that may serve to support the rail.
- An act of thwarting; something which thwarts; a hindrance, an obstacle.
- To cause to fail; to frustrate, to prevent.
- To place (something) across (another thing); to position crosswise.
- To hinder or obstruct by placing (something) in the way of; to block, to impede, to oppose.
- To move (something) across or counter to; to cross.