The most common and most likely answer to this crossword clue is the 8 letter word THEMATIC
I've seen this crossword clue in Independent
T
H
E
M
A
T
I
C
More clues leading to the result THEMATIC
- Like unmentionables here in broadcast chat item
- Those people at reserve, not fully adhering to topic
- The thoughtless take car out, in accordance with recurrent idea
- On subject of people2 almost caught
- Relating to a subject — one that’s generally taught seeing ma’s not around
- The graduate a short time in charge of certain subject
- Match tie, ordered as part of a set?
- Article, one going into most of game following a recurrent idea?
- Topical item chat sorted out
Buddy explains!

The straight part
We know that "adhering to topic" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case adhering to topic = thematic.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 THEMATIC mean?
THEMATIC noun- A postage stamp that is part of a thematic collection.
- Relating to, or having a theme or a topic.
- Relating to a melodic subject.
- Of a word stem, ending in a vowel that appears in or otherwise influences the noun or verb's inflection.
- (history) Of or relating to a theme.