In part onshore, a charity having influence (5)
I believe the answer is:
reach
'influence' is the definition.
(thesaurus)
'in part onshore a charity' is the wordplay.
'in part' indicates the answer is hidden within the clue.
'REACH' is hidden in the letters of 'onshore a charity'.
'having' acts as a link.
(Other definitions for reach that I've seen before include "Arrive at the destination" , "Put out the hand for a part of the river" , "Extend an arm" , "Limits within which something can be effective" , "Hands up" .)