Very demanding wordplay I have put round it (8)
I believe the answer is:
punitive
'very demanding' is the definition.
(I've seen this before)
'wordplay i have put round it' is the wordplay.
'wordplay' becomes 'pun' (synonyms).
'i have' becomes 'I've' (contraction of 'I have').
'put round' indicates putting letters inside.
'pun'+'ive'='punive'
'punive' placed around 'it' is 'PUNITIVE'.
(Other definitions for punitive that I've seen before include "Intended to inflict punishment" , "Severe and retaliatory" , "As deterrent, retribution" , "Inflicting penalties" , "very demanding" .)