The most common and most likely answer to this crossword clue is the 10 letter word GOOSEFLESH
I've seen this crossword clue in Financial Times
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More clues leading to the result GOOSEFLESH
Buddy explains!
The straight part
We know that "Reaction to cold in Gander?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case reaction to cold in gander? = gooseflesh.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 GOOSEFLESH mean?
GOOSEFLESH noun- (chiefly in plural) Raised skin, usually caused by the involuntary erection of hairs on the neck or arms caused by cold, excitement, or fear.