Blimps regularly track aircraft (7)
I believe the answer is:
biplane
'aircraft' is the definition.
(biplane is a kind of aircraft)
'blimps regularly track' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'track' becomes 'lane'.
The alternate letters of 'blimps' are 'bip'.
'bip'+'lane'='BIPLANE'
(Other definitions for biplane that I've seen before include "Early aircraft" , "Eg, Tiger Moth" , "Aircraft with double wings" , "craft" , "flying machine" .)