Stingy priest clutching the writer's promissory notes (12)
I believe the answer is:
parsimonious
'stingy' is the definition.
(similar in meaning)
'priest clutching the writer's promissory notes' is the wordplay.
'priest' becomes 'parson'.
'clutching' indicates putting letters inside.
'the writer's' becomes 'Im' ('I am' referring to the writer of the clue).
'promissory notes' becomes 'ious' (IOU is an example).
'parson' enclosing 'im' is 'parsimon'.
'parsimon'+'ious'='PARSIMONIOUS'
(Other definitions for parsimonious that I've seen before include "Miserly" , "Frugal" , "Cheese-paring" , "Thrifty, mean" , "Penny-pinching" .)