Expect to lose half printing speed (10)
I believe the answer is:
expedition
'speed' is the definition.
(expedition is a kind of speed)
'expect to lose half printing' is the wordplay.
'to lose half' suggests halving the letters.
'printing' becomes 'edition' (a particular edition of something printed).
'expect' with half the letters taken is 'exp'.
'exp'+'edition'='EXPEDITION'
(Other definitions for expedition that I've seen before include "Voyagers" , "Quest" , "alacrity" , "Speed is the essence" , "haste" .)