The most common and most likely answer to this crossword clue is the 7 plus 1 letter word ENDORSE E
I've seen this crossword clue in Independent
E
N
D
O
R
S
E
E
Buddy explains!
The straight part
We know that "back" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case back = endorse e.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 ENDORSE E mean?
ENDORSE E noun- The person to whom something is transferred by endorsement.