The most common and most likely answer to this crossword clue is the 9 letter word LOOKALIKE
I've seen this crossword clue in The Guardian
L
O
O
K
A
L
I
K
E
More clues leading to the result LOOKALIKE
- Double trouble in lake with oil incurring fine
- Double oil leak? OK, that’s awful
- Double I, double K, double O, double L, a different E
- Can goddess dishearten Kylie’s 29er?
- Appear to relish swallowing a double
- 2K ringmaster’s invested in in port makes double
- Double first in archaeology — be keen on following fashion
- Hey, vodka’s back: fancy double?
Buddy explains!

The straight part
We know that "29er? /29er" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case 29er? /29er = lookalike.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 LOOKALIKE mean?
LOOKALIKE noun- Someone who physically resembles (looks like) someone else.