Useless computers holding writer back (5)
I believe the answer is:
inept
'useless' is the definition.
(thesaurus)
'computers holding writer back' is the wordplay.
'computers' becomes 'it' (information technology).
'holding' means one lot of letters goes inside another.
'writer' becomes 'pen' (I've seen this before).
'back' says the letters should be written in reverse.
'pen' back-to-front is 'nep'.
'it' enclosing 'nep' is 'INEPT'.
(Other definitions for inept that I've seen before include "Showing a lack of competence" , "Awkward, showing no skill" , "Unskilful or unsuitable" , "Amateurish" , "Lacking skill" .)