Initially, bear a hazard, as lively (5)
I believe the answer is:
brisk
'lively' is the definition.
(I've seen this before)
'initially bear a hazard' is the wordplay.
'initially' says to take the initial letters.
'a hazard' becomes 'risk' ('risk' can be a synonym of 'hazard').
The first letter of 'bear' is 'b'.
'b'+'risk'='BRISK'
'as' acts as a link.
(Other definitions for brisk that I've seen before include "Quick and invigorating" , "Quick, active, energetic" , "Bustling" , "Spry" , "Vigorous" .)