The most common and most likely answer to this crossword clue is the 7 letter word LAGGING
I've seen this crossword clue in The Guardian
L
A
G
G
I
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Buddy explains!
The straight part
We know that "Trailing/insulation" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case trailing/insulation = lagging.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 LAGGING mean?
LAGGING verb- To fail to keep up (the pace), to fall behind
- To cover (for example, pipes) with felt strips or similar material (referring to a time lag effect in thermal transfer)
- To transport as a punishment for crime.
- To cause to lag; to slacken.
- The covering of something with strips of felt, wood etc, either as insulation or for protection.
- The material so used.
- A prison sentence.
- Falling behind, not keeping up the pace
- Occurring after; indicating the later phase of