Lose extremely sharp spike on motorway (8)
I believe the answer is:
misplace
'lose' is the definition.
(to misplace something is to lose it)
'extremely sharp spike on motorway' is the wordplay.
'extremely' means to remove the middle letters (only the extremes of the word are used).
'spike' becomes 'lace' (synonyms).
'on' says to put letters next to each other.
'motorway' becomes 'MI' (resembles Ml, English motorway).
'sharp' with its centre taken out is 'sp'.
'sp'+'lace'='splace'
'splace' after 'mi' is 'MISPLACE'.
(Other definitions for misplace that I've seen before include "Set in the wrong position" , "Lose temporarily - put in wrong location" , "Be unable to find" , "Wrongly put - lose" , "Mislay" .)