Since worker's touring around America (7)
I believe the answer is:
because
'since' is the definition.
(I've seen this before)
'worker's touring around america' is the wordplay.
'worker' becomes 'bee' (a worker bee).
'touring' is an insertion indicator (tour can mean to go around).
'around' becomes 'ca' (circa).
'america' becomes 'US' (United States).
'ca'+'us'='caus'
'bee' going around 'caus' is 'BECAUSE'.
(Other definitions for because that I've seen before include "Thanks to this" , "Beginning to explain" , "For the reason that" , "On account of" , "Owing to" .)