Dic: have one's hand in, have a hand in

have one's hand in something:
Fig. to exercise control over something; to play an identifiable role in doing something. (See also have a hand in something.)

• She always has to have her hand in everything.
• I want to have my hand in the arrangement.

.... McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

have a hand in something: to be involved in something

• The party was basically Kim's idea but I think Lisa had a hand in it too.

.... Cambridge Idioms Dictionary,

have a hand in doing something: to take part in an activity

• We don't put our label on anything unless we have a hand in designing and producing it.

... Cambridge Dictionary of American Idioms

http://idioms.thefreedictionary.com/hand