Parking behind college a considerable distance (6)
I believe the answer is:
parsec
'a considerable distance' is the definition.
'parsec' can be an answer for 'distance' (I've seen this before). I am not certain of the 'a considerable' bit.
'parking behind college' is the wordplay.
'parking' becomes 'p' (abbreviation on road signs).
'behind' becomes 'arse' (both can mean the buttocks).
'college' becomes 'c'.
'p'+'arse'+'c'='PARSEC'
Can you help me to learn more?
(Other definitions for parsec that I've seen before include "3.26 light years" , "far in the distance" , "Astronomical length - scrape (anag)" , "fair distance" , "Enormous distance" .)