Casually play Street Spirit (5)
I believe the answer is:
strum
'casually play' is the definition.
(strum a guitar)
'street spirit' is the wordplay.
'street' becomes 'st' (abbreviation).
'spirit' becomes 'rum' (alcoholic spirit).
'st'+'rum'='STRUM'
(Other definitions for strum that I've seen before include "'Sound the strings, musically (5)'" , "Play with sweeps of fingers" , "Play a stringed instrument (badly)" , "Play strings with sweep of hand" , "Play idly on guitar etc" .)