Delight as first of penthouses let (6)
I believe the answer is:
please
'delight' is the definition.
(I know that delight is a more specific form of delight)
'first of penthouses let' is the wordplay.
'first of penthouses' becomes 'p' (1st letter of 'penthouses').
'let' becomes 'lease' (as in to lease or let a building).
'p'+'lease'='PLEASE'
'as' acts as a link.
(Other definitions for please that I've seen before include "Give pleasure to (someone)" , "Entertain" , "Polite word of request" , "if you don't mind" , "Gratify, make contented" .)