Relative is foul when last two letters never arrive (5)

I believe the answer is:

uncle

'relative' is the definition.
(uncle is a kind of relative)

I don't understand how the remainder of the clue works.

(Other definitions for uncle that I've seen before include "Male relative - pawnbroker" , "Pawnbroker (sl.)" , "older relative" , "Grandfather's son" , "Male relation; pawnbroker" .)

I've seen this clue in The Times.

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