Mobile service provider without ties, according to Danny Dyer? (5)

I believe the answer is:
three
'mobile' is the definition.
Both the definition and answer are adjectives. Perhaps they are linked in a way I don't understand?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for three that I've seen before include "Prime number" , "trilogy" , "Number of Furies or Norns" , "Bears or blind mice" , "Number of Dumas's musketeers" .)
