Use trade fair to showcase large computer systems (7)
I believe the answer is:
exploit
'use' is the definition.
(exploiting is a kind of using)
'trade fair to showcase large computer systems' is the wordplay.
I cannot really see how this works, but
'large' could be 'l' and 'l' is found in the answer.
'fair' could be 'expo' (an expo is a type of large exhibition) and 'expo' is present in the remaining letters.
'computer systems' could be 'it' (I've seen this in other clues) and 'it' is present in the answer.
No letters remain.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for exploit that I've seen before include "Make full use of" , "Make capital out of" , "Make use of - achievement" , "Heroic achievement" , "Adventure, bold or notable deed" .)