The most common and most likely answer to this crossword clue is the 8 letter word GREEDIER
I've seen this crossword clue in Independent
G
R
E
E
D
I
E
R
More clues leading to the result GREEDIER
Buddy explains!

The straight part
We know that "comparatively selfish" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case comparatively selfish = greedier.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 GREEDIER mean?
GREEDIER adjective- Having greed; consumed by selfish desires.
- Prone to overeat.
- Tending to match as much text as possible.
- (of an algorithm) That tries to find the global optimum by finding the local optimum at each stage.