It holds writer back being useless (5)
I believe the answer is:
inept
'useless' is the definition.
(I've seen this before)
'it holds writer back' is the wordplay.
'it' becomes ''t' (abbreviation. e.g. in 'tis).
'holds' is a charade indicator (letters next to each other).
'writer' becomes 'peni' (I can't explain this - if you can you should give a lot more credence to this answer).
'back' shows that the letters should be reversed in order.
't'+'peni'='tpeni'
'tpeni' back-to-front is 'INEPT'.
'being' acts as a link.
Can you help me to learn more?
(Other definitions for inept that I've seen before include "Silly - unskilled - unsuitable" , "Standard required in a piece of work (colloq.)" , "Lacking skill" , "rubbish" , "Lousy" .)