The most common and most likely answer to this crossword clue is the 8 letter word FLAGGING
I've seen this crossword clue in The Times
F
L
A
G
G
I
N
G
More clues leading to the result FLAGGING
Buddy explains!

The straight part
We know that "Weak/semaphore?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case weak/semaphore? = flagging.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 FLAGGING mean?
FLAGGING verb- To furnish or deck out with flags.
- To mark with a flag, especially to indicate the importance of something.
- (often with down) To signal to, especially to stop a passing vehicle etc.
- To convey (a message) by means of flag signals.
- (often with up) To note, mark or point out for attention.
- To signal (an event).
- To set a program variable to true.
- To decoy (game) by waving a flag, handkerchief, etc. to arouse the animal's curiosity.
- To penalize for an infraction.
- To defeat (an opponent) on time, especially in a blitz game.
- To weaken, become feeble.
- To hang loose without stiffness; to bend down, as flexible bodies; to be loose, yielding, limp.
- To let droop; to suffer to fall, or let fall, into feebleness.
- To enervate; to exhaust the vigour or elasticity of.
- To pave with flagstones.
- A pavement or sidewalk of flagstones; flagstones, collectively.
- The process by which something flags or tires.