Police almost there crashed aircraft (10)
I believe the answer is:
helicopter
'aircraft' is the definition.
(helicopter is a kind of aircraft)
'police almost there crashed' is the wordplay.
'almost' means to remove the last letter (almost the whole word is kept).
'crashed' indicates an anagram.
'there' with its final letter removed is 'ther'.
'police'+'ther'='policether'
'policether' with letters rearranged gives 'HELICOPTER'.
(Other definitions for helicopter that I've seen before include "aircraft" , "surveillance equipment" , "Chopper" , "Flier" , "Rotary-winged craft" .)