Chemical secretion increasingly reflected in dial (9)
I believe the answer is:
pheromone
'chemical secretion' is the definition.
The definition suggests a singular noun which matches the answer.
'increasingly reflected in dial' is the wordplay.
'increasingly' becomes 'more'.
'reflected' is a reversal indicator (letters reflected back).
'in' indicates putting letters inside.
'dial' becomes 'phone' (I've seen this in another clue).
'more' in reverse letter order is 'erom'.
'erom' put inside 'phone' is 'PHEROMONE'.
Can you help me to learn more?
(Other definitions for pheromone that I've seen before include "Chemical affecting behaviour" , "What attracts" , "Chemical attractor" , "Chemical signal between organisms" , "Substance secreted that affects others of same species" .)