Isolated nurses returning, provided preparation to prevent infestation carried out quickly (5-4)

'carried out quickly' is the definition.

'isolated nurses returning provided preparation to prevent infestation' is the wordplay.
'isolated' becomes 'rare'.
'nurses' is an insertion indicator (nurse can mean to hold onto or harbour).
'returning' is a reversal indicator.
'provided' becomes 'if'.
'preparation to prevent infestation' becomes 'dip' (sheep dip is used to prevent infestations in sheep).
'if'+'dip'='ifdip'
'ifdip' back-to-front is 'pidfi'.
'rare' going around 'pidfi' is 'RAPID-FIRE'.