The most common and most likely answer to this crossword clue is the 8 letter word USERNAME
I've seen this crossword clue in The Times
U
S
E
R
N
A
M
E
More clues leading to the result USERNAME
- American eagle that's caught in the morning gets form of identification
- Locked up by policeman, resubmit access code
- Electronic tag?
- Junkie turned over European dude to get online identity
- Identification of aggressive man resulted in retreat
- Mean ruse perhaps needed to get online access
- Section of code man resurrected brought up ID
- Unique address where menus are developed
- Nurse stupidly given a setter’s online ID
- Subject to review, policeman resumes keeping computer ID
Buddy explains!

The straight part
We know that "form of identification" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case form of identification = username.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does USERNAME mean?
USERNAME noun- A person's identification on an individual computer system.