Complete quiet always for poet (5)
I believe the answer is:
sheer
'complete' is the definition.
(I've seen this before)
'quiet always for poet' is the wordplay.
'quiet' becomes 'sh' ('sh' is used to tell someone to be quiet).
'always for poet' becomes 'eer' (archaic or poetic version of 'ever').
'sh'+'eer'='SHEER'
(Other definitions for sheer that I've seen before include "Almost perpendicular or very thin" , "Steep; fine" , "Very fine like silk stockings" , "avoid an unpleasant thing" , "Deviate (from) - vertical" .)