The most common and most likely answer to this crossword clue is the 7 letter word CUCKOLD
I've seen this crossword clue in The Guardian
C
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More clues leading to the result CUCKOLD
Buddy explains!
The straight part
We know that "fellow whose wife has cheated" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fellow whose wife has cheated = cuckold.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 CUCKOLD mean?
CUCKOLD noun- A man married to an unfaithful wife, especially when he is unaware or unaccepting of the fact.
- A West Indian plectognath fish, Rhinesomus triqueter.
- The scrawled cowfish, Acanthostracion quadricornis and allied species.
- To make a cuckold or cuckquean of someone by being unfaithful, or by seducing their partner or spouse.