They leapt about using thought transfer (9)
I believe the answer is:
telepathy
'thought transfer' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Maybe you can see a link between them that I don't see?
'they leapt about' is the wordplay.
'about' indicates anagramming the letters.
'they'+'leapt'='theyleapt'
'theyleapt' with letters rearranged gives 'TELEPATHY'.
'using' is the link.
Can you help me to learn more?
(Other definitions for telepathy that I've seen before include "Extrasensory communication" , "Sixth sense" , "Communication from one mind to another, no speech" , "Apparent non-verbal communication" , "Ability to read someone's mind" .)