Read duties involved nursing duke (7)
I believe the answer is:
studied
'read' is the definition.
(I've seen this before)
'duties involved nursing duke' is the wordplay.
'involved' indicates an anagram (involved can mean confusing or complex).
'nursing' is an insertion indicator.
'duke' becomes 'd'.
'duties' anagrammed gives 'stuied'.
'stuied' going around 'd' is 'STUDIED'.
(Other definitions for studied that I've seen before include "Learnt by reading" , "Looked at closely" , "Read" , "deliberate" , "Considered, learnt about" .)