The most common and most likely answer to this crossword clue is the 6 letter word DILATE
I've seen this crossword clue in The Sunday Telegraph
D
I
L
A
T
E
More clues leading to the result DILATE
- Call a number on the phone to speak at length
- Get bigger Detective Inspector in front of deceased
- Spread for which I'd turned up behind schedule
- Enlarge muscle; fail to keep it
- Stretch to live long, they say
- Senior copper and others rejected spread
- Swell rendezvous in France he interrupts
- Fish brought back recently get spread out
- Little girl slow to develop
- Spread out hat that’s turned over and put away
Buddy explains!
The straight part
We know that "that’s what growing pupils do" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case that’s what growing pupils do = dilate.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 DILATE mean?
DILATE verb- To enlarge; to make bigger.
- To become wider or larger; to expand.
- To speak largely and copiously; to dwell in narration; to enlarge; with "on" or "upon".
- To use a dilator to widen (something, such as a vagina).
- (dismissal, 4chan) Expression of anger and contempt, specifically at transgender women.