Gelatinous substance again missing in recipe, initially (4)

I believe the answer is:

agar

I'm a little stuck... Click here to teach me more about this clue!

'gelatinous substance' is the definition.
(I've seen this in another clue)

'again missing in recipe initially' is the wordplay.
'again missing in' becomes 'aga' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'initially' suggests taking the first letters.
The first letter of 'recipe' is 'r'.
'aga'+'r'='AGAR'

Can you help me to learn more?

(Other definitions for agar that I've seen before include "Jelly medium" , "Jelly got from seaweeds, used in foods" , "Substance derived from seaweed" , "a newspaper rejected" , "Medium for growth" .)

I've seen this clue in The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.