Former priest accommodated by sanctimonious old American (8)
I believe the answer is:
previous
'former' is the definition.
(synonyms)
'priest accommodated by sanctimonious old american' is the wordplay.
'priest' becomes 'rev'.
'accommodated by' is an insertion indicator.
'sanctimonious' becomes 'pi'.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'american' becomes 'us' (abbreviation for United States).
'rev' put into 'pi' is 'previ'.
'previ'+'o'+'us'='PREVIOUS'
(Other definitions for previous that I've seen before include "Overhasty; existing earlier" , "Overly hasty in acting or in drawing a conclusion" , "Foregoing" , "form" , "Earlier, occasion say" .)