The most common and most likely answer to this crossword clue is the 2 plus 2 letter word HI FI
I've seen this crossword clue in Financial Times
H
I
F
I
More clues leading to the result HI FI
Buddy explains!
The straight part
We know that "Reproductive system" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case reproductive system = hi fi.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 HI FI mean?
HI FI noun- High fidelity