Manual worker right — there's an unpleasant smell inside (8)
I believe the answer is:
handbook
'manual' is the definition.
(instruction manual)
'worker right there's an unpleasant smell inside' is the wordplay.
'worker' becomes 'hand' (hand is a kind of worker).
'right' becomes 'ok' (both are affirmative answers).
'there's an unpleasant smell' becomes 'BO' (informal abbreviation for body odour).
'inside' means one lot of letters goes inside another.
'hand'+'ok'='handok'
'handok' going around 'bo' is 'HANDBOOK'.
(Other definitions for handbook that I've seen before include "Guide" , "companion" , "Manual, reference" .)