On line, he's involved in a crooked deal (7)
I believe the answer is:
leashed
'a crooked deal' is the definition.
The answer and definition are not the same part of speech. However, adjectives and past participle verbs can sometimes define each other.
'on line he's involved in' is the wordplay.
'on line' becomes 'lead' (lead line is a kind of line. I am not sure about the 'on' bit.).
'involved' indicates an anagram (involved can mean confusing or complex).
'in' is an insertion indicator.
'hes' is an anagram of 'she'.
'lead' enclosing 'she' is 'LEASHED'.
Can you help me to learn more?
(Another definition for leashed that I've seen is " restricted".)