The most common and most likely answer to this crossword clue is the 8 letter word CAMPAIGN
I've seen this crossword clue in The Guardian
C
A
M
P
A
I
G
N
More clues leading to the result CAMPAIGN
- Crusade Conservative politician is entering again, sadly
- Conservative politician coming in again ruined approach to election
- Frequently clap MEP, making an effort to secure votes
- Returning computer nuisance, it’s said, in military operations
- Offensive politician a soldier knocked over in the loo?
- … to cast magic over father’s new crusade
- Drunk, pacing around all morning, becomes offensive
- Conservative MP gets in again after changing crusade
- Lobby for Conservative politician to capture a potential gain
- Offensive Conservative politician gets in again after bruising
Buddy explains!

The straight part
We know that "crusade" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case crusade = campaign.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 CAMPAIGN mean?
CAMPAIGN noun- A series of operations undertaken to achieve a set goal.
- The period during which a blast furnace is continuously in operation.
- An open field; a large, open plain without considerable hills; a champaign.
- An excursion into the countryside.
- To take part in a campaign.
- Consistently ride in races for a racing season.