Coppers to arrest socialist outside church as priority (10)

'priority' is the definition.
(precedence is a kind of priority)

'coppers to arrest socialist outside church' is the wordplay.
'coppers' becomes 'pence' (I've seen this before).
'to arrest' is an insertion indicator.
'socialist' becomes 'red' (red is a kind of socialist**).
'outside' indicates putting letters inside.
'church' becomes 'ce' (abbreviation for Church of England).
'red' going around 'ce' is 'reced'.
'pence' going around 'reced' is 'PRECEDENCE'.

'as' acts as a link.