In the garden, he adds a touch of imagination (5)
I believe the answer is:
gnome
This clue might be a double definition.
'in the garden he adds a' is the first definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'touch of imagination' is the second definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps there's an association between them I don't understand?
Can you help me to learn more?
(Other definitions for gnome that I've seen before include "Dwarfish creature; garden ornament" , "Creature in garden (or Zurich?)" , "Little garden man?" , "Hobgoblin" , "Swiss financier" .)