Perfectionist finding swab originally left inside heart (8)
I believe the answer is:
stickler
'perfectionist' is the definition.
(I've seen this before)
'swab originally left inside heart' is the wordplay.
'originally' suggests taking the first letters.
'left' becomes 'l' (common abbreviation).
'inside' indicates putting letters inside.
'heart' becomes 'ticker' (synonyms).
The initial letter of 'swab' is 's'.
'l' put within 'ticker' is 'tickler'.
's'+'tickler'='STICKLER'
'finding' is the link.
(Other definitions for stickler that I've seen before include "One's insistent" , "Punctilious, insistent person" , "I may do that precisely" , "One fastidiously insists on something" , "Pernickety person" .)