Bluejay regularly seen in meadow (3)
I believe the answer is:
lea
'meadow' is the definition.
(a lea is a grassy area)
'bluejay regularly seen' is the wordplay.
'regularly seen' indicates alternate letters.
The alternate letters of 'bluejay' are 'LEA'.
'in' acts as a link.
(Other definitions for lea that I've seen before include "Tract of pastureland" , "Open grassy land; river" , "River of east London" , "'The lowing herd wind slowly o'er the . . .'" , "Grass area" .)