Fabricate without force unusual micro-organisms (8)
I believe the answer is:
bacteria
'micro-organisms' is the definition.
(I've seen this before)
'fabricate without force unusual' is the wordplay.
'without' is a deletion indicator.
'force' becomes 'f' (abbreviation in physics e.g. f=ma).
'unusual' indicates an anagram.
'fabricate' with 'f' taken out is 'abricate'.
'abricate' anagrammed gives 'BACTERIA'.
(Other definitions for bacteria that I've seen before include "Microscopic organisms, may cause disease" , "Care a bit about these micro-organisms" , "Microscopic organisms, good and bad" , "Tiny causes of disease" , "These single-cell organisms are in bait race" .)