Roaming free in gale rat perished (2,5)

I believe the answer is:

at large

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'roaming free' is the definition.

'gale rat perished' is the wordplay.
'gale rat' can be anagrammed to 'AT LARGE'.
Though, I'm unsure how this is indicated.

'in' acts as a link.

Can you help me to learn more?

(Other definitions for at large that I've seen before include "Escaped; as a whole" , "Free to roam about, not in confinement" , "Escaped, not captured" , "Escaped; not yet caught" , "On the loose, at liberty" .)

I've seen this clue in The Sun.

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