Could he arrange for the king to have a little extra height? (6)
I believe the answer is:
knight
'could he arrange for' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'king to have a little extra height?' is the wordplay.
I cannot really understand how this works, but
an anagram of 'king' is 'knig' which is present in the answer.
'height?' could be 'ht' (abbreviation) and 'ht' is found within the answer.
This accounts for all the letters.
This explanation may well be incorrect...
'the' is the link.
Can you help me to learn more?
(Other definitions for knight that I've seen before include "cavalier" , "board member" , "One entitled to use "Sir"" , "Heroic champion" , "Gallant" .)