Reportedly instructed to be stretched (4)
I believe the answer is:
taut
'be stretched' is the definition.
(I've seen this before)
'reportedly instructed' is the wordplay.
'reportedly' shows a homophone (sound like).
'instructed' becomes 'taught' ('teach' can be a synonym of 'instruct').
'taught' is a homophone of 'TAUT'.
'to' acts as a link.
(Other definitions for taut that I've seen before include "On the slope" , "Held in tension" , "Fully stretched" , "Stretched, pulled tight" , "Stretched tight or disciplined" .)