Somehow uncap item using air (9)
I believe the answer is:
pneumatic
'using air' is the definition.
(I've seen this before)
'somehow uncap item' is the wordplay.
'somehow' indicates anagramming the letters.
'uncap'+'item'='uncapitem'
'uncapitem' anagrammed gives 'PNEUMATIC'.
(Other definitions for pneumatic that I've seen before include "Type of drill" , "Operated by pressurised gas" , "Concerned with air, gases or wind" , "form of drill?" , "Using compressed air" .)