The most common and most likely answer to this crossword clue is the 6 letter word FENDER
F
E
N
D
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Buddy explains!
The straight part
We know that "Guard" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case guard = fender.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 FENDER mean?
FENDER noun- Panel of a car which encloses the wheel area, especially the front wheels
- A shield, usually of plastic or metal, on a bicycle that protects the rider from mud or water
- Any shaped cushion-like object normally made from polymers, rubber or wood that is placed along the sides of a boat to prevent damage when moored alongside another vessel or jetty, or when using a lock, etc. Modern variations are cylindrical although older wooden version and rubbing strips can still be found; old tyres are used as a cheap substitute
- A low metal framework in front of a fireplace, intended to catch hot coals, soot, and ash
- To use fenders to protect the side of a boat