Was lazy, but maybe did about half a mile (5)
I believe the answer is:
idled
'was lazy' is the definition.
(to idle is to be lazy or do nothing)
'maybe did about half a mile' is the wordplay.
'maybe' indicates anagramming the letters.
'about' means one lot of letters goes inside another.
'half a' suggests halving the letters.
'did' is an anagram of 'idd'.
'mile' with half the letters taken is 'le'.
'idd' going around 'le' is 'IDLED'.
'but' acts as a link.
(Other definitions for idled that I've seen before include "Wasted time" , "sat back" , "Spent time doing nothing" , "(Of an engine) ran slowly out of gear" , "Lazed around" .)