Insect by herself at last over meadow (4)
I believe the answer is:
flea
'insect' is the definition.
(flea is a kind of insect)
'herself at last over meadow' is the wordplay.
'at last' indicates one should take the final letters.
'over' says to put letters next to each other.
'meadow' becomes 'lea' (I've seen this before**).
The last letter of 'herself' is 'f'.
'f'+'lea'='FLEA'
'by' acts as a link.
(Other definitions for flea that I've seen before include "Blood-sucking parasites" , "Jumping parasite" , "In one's ear, it's a stinging rebuke" , "Bug" , "Small blood-sucking insect" .)