Peter's involved with Meryl (6)
I believe the answer is:
streep
'meryl' is the definition.
I know nothing about this answer so I can't tell whether this works.
'peter's involved' is the wordplay.
'involved' indicates an anagram (involved can mean confusing or complex).
'peters' is an anagram of 'STREEP'.
'with' acts as a link.
Can you help me to learn more?
(Other definitions for streep that I've seen before include "Meryl - - (films)" , "Inflamed swelling inside" , "Meryl -, US actress" , "See 4 Down" , "Film star in The Iron Lady, b. 1949" .)