Occasional worker from a small university in California (6)
I believe the answer is:
casual
'occasional worker' is the definition.
(a casual worker works from time to time)
'a small university in california' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'university' becomes 'U' (abbreviation as in UMass).
'in' indicates putting letters inside.
'california' becomes 'cal' (short for California).
'a'+'s'+'u'='asu'
'asu' put within 'cal' is 'CASUAL'.
'from' acts as a link.
(Other definitions for casual that I've seen before include "Informal or temporary" , "Relaxed - unintentional" , "Negligent" , "Of clothes, not formal" , "Informal or cursory" .)