The most common and most likely answer to this crossword clue is the 6 letter word PENTAD
P
E
N
T
A
D
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The straight part
We know that "G5 lot" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case g5 lot = pentad.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 PENTAD mean?
PENTAD noun- A group or series of five things.
- A mean average value of temperature, etc., taken every five days.
- Any element, atom, or radical having a valence of five, or which can be combined with, substituted for, or compared with, five atoms of hydrogen or other monad.