In lemon squash, a bit of thymol as medicinal ingredient (7)
I believe the answer is:
menthol
'medicinal ingredient' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe there's a link between them I don't understand?
'in lemon squash a bit of thymol' is the wordplay.
'in' is an insertion indicator.
'squash' is an anagram indicator (I've seen this in other clues).
'a bit of thymol' becomes 'th' (I can't justify this - if you can you should give a lot more credence to this answer).
'lemon' with letters rearranged gives 'menol'.
'menol' going around 'th' is 'MENTHOL'.
'as' is the link.
Can you help me to learn more?
(Other definitions for menthol that I've seen before include "Peppermint oil derivative" , "mild analgesic" , "Soothing substance from peppermint" , "Peppermint camphor" , "Chemical compound that smells like mint" .)