Sir Thomas, joined by Stan at the tube station (4)
I believe the answer is:
more
'sir thomas' is the definition.
(I've seen this in another clue)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for more that I've seen before include "Writer" , "author" , "Greater quantity or number" , "Extra (for Sir Thomas?)" , "See 9" .)