Mentally prepare pup circling outskirts of shady church (5,2)

'mentally prepare' is the definition.
(to psych up is to prepare psychologically)

'pup circling outskirts of shady church' is the wordplay.
'circling' means one lot of letters goes inside another (circling can mean going around or containing).
'outskirts of' says to hollow out the word (remove centre letters).
'church' becomes 'ch' (common abbreviation).
'shady' with its middle removed is 'sy'.
'sy'+'ch'='sych'
'pup' enclosing 'sych' is 'PSYCH UP'.