Fills bus to be taken on tour, making them extremely happy (8)
I believe the answer is:
blissful
'extremely happy' is the definition.
(I've seen this before)
'fills bus to be' is the wordplay.
'to be' indicates anagramming the letters.
'fills'+'bus'='fillsbus'
'fillsbus' anagrammed gives 'BLISSFUL'.
'taken on tour making them' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for blissful that I've seen before include "Completely happy and contented" , "Happy, often delusively" , "Full of joy" , "Ecstatic, rapturously happy" , "Joyous, rapt" .)