What can secure speed of coral formation? (4-5)
I believe the answer is:
reef-knots
'what' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'speed of coral formation?' is the wordplay.
I cannot quite understand how this works, but
'speed' could be 'knot' (knot is a nautical measure of speed) and 'knot' is found within the answer.
'formation?' could be 'reef' (reef is a kind of formation) and 'reef' is located in the answer.
A single letter 's' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
'can secure' acts as a link.
Can you help me to learn more?
(Other definitions for reef-knots that I've seen before include "Rope manipulations for ref tokens, strong and secure" , "Simple way of joining ends of strings" , "Ties made of two half hitches" , "They are tied using symmetrical loops" .)