I had been in front, but became lazy (5)
I believe the answer is:
idled
'lazy' is the definition.
(I've seen this before)
'i had been in front' is the wordplay.
'i had' becomes 'i'd' (contraction).
'been in front' becomes 'led' (to lead is to go in front).
'id'+'led'='IDLED'
'but became' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for idled that I've seen before include "Was lazy" , "Spent time doing nothing" , "Lazed around" , "Wasted time" , "pottered" .)