Plunged through it, I had, when it split (7)
I believe the answer is:
divided
'split' is the definition.
(similar in meaning)
'plunged through it i had when it' is the wordplay.
I cannot quite understand how this works, but
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is found in the answer.
'i' is within the answer.
'had' could be 'd' (I've seen this in other clues) and 'd' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for divided that I've seen is " riven by dissent".)