The most common and most likely answer to this crossword clue is the 7 letter word BOOSTER
I've seen this crossword clue in Financial Times
B
O
O
S
T
E
R
More clues leading to the result BOOSTER
Buddy explains!
The straight part
We know that "Something to increase the effectiveness" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case something to increase the effectiveness = booster.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 BOOSTER mean?
BOOSTER noun- Something that boosts.
- The first stage of a multistage rocket that provides the thrust for liftoff and the initial flight
- A motor-generator set used for voltage regulation in direct current electrical power circuits.
- Someone who is a fan or supporter of something.
- Someone who promotes a town or business
- A member of a booster club.
- A booster dose.
- A term that serves to amplify or strengthen an utterance, such as "really".
- A power-up item.
- A package of cards or figurines designed to add to a player's collection.
- A thief.