Starchy class at Lancing originally (6)
I believe the answer is:
formal
'starchy' is the definition.
('formal' can be similar in meaning to 'starchy')
'class at lancing originally' is the wordplay.
'class' becomes 'form' (form class is a kind of class**).
'originally' indicates taking the first letters.
The initial letters of 'at lancing' is 'al'.
'form'+'al'='FORMAL'
(Other definitions for formal that I've seen before include "Conforming to accepted rules or customs" , "Suitable for a ceremonial occasion" , "Stately or official" , "Done in accordance with etiquette" , "conventionally correct" .)