Cardinal, no Saint, needing drink (6)
I believe the answer is:
thirty
'cardinal' is the definition.
(similar in meaning)
'no saint needing drink' is the wordplay.
'no' suggests deleting specific letters.
'saint' becomes 's'.
'needing drink' becomes 'thirsty' (someone thirsty is in need of a drink).
'thirsty' with 's' removed is 'THIRTY'.
(Other definitions for thirty that I've seen before include "Score and a half" , "Number of pieces of silver paid to Judas" , "Number of across clues in this puzzle" , "Half of threescore" , "November's days" .)