Ring, having more trouble getting stimulant (9)
I believe the answer is:
pheromone
'stimulant' is the definition.
Both the answer and definition are singular nouns.
Maybe they are linked in a way I don't understand?
'ring having more trouble' is the wordplay.
'ring' becomes 'phone' (synonyms).
'having' means one lot of letters goes inside another.
'trouble' is an anagram indicator.
'more' anagrammed gives 'erom'.
'phone' going around 'erom' is 'PHEROMONE'.
'getting' acts as a link.
Can you help me to learn more?
(Other definitions for pheromone that I've seen before include "What attracts" , "Chemical signal between organisms" , "Chemical affecting behaviour" , "Chemical attractor" , "Substance secreted that affects others of same species" .)