Good little fairies getting hold of old Dutch spells (7)
I believe the answer is:
periods
'spells' is the definition.
'good little fairies getting hold of old dutch' is the wordplay.
'good little fairies' becomes 'peris'.
'getting hold of' indicates putting letters inside.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'dutch' becomes 'd' (common abbreviation).
'o'+'d'='od'
'peris' going around 'od' is 'PERIODS'.
(Other definitions for periods that I've seen before include "Stops" , "School lessons" .)