The most common and most likely answer to this crossword clue is the 2 letter word HI
I've seen this crossword clue in The Times
H
I
More clues leading to the result HI
- Sitcom of one hour, back on screen
- Snag besetting European using latest devices
- Something for the home that’s welcome if retiring
- Pelt and strike endless camp show
- Sound equipment taken out of church if irritating
- Space-age couple storing energy
- Delhi final has the sound of quality
- Hello when echoed by sound equipment
- Sophisticated science a knockout with EU executives
- Hardy Amies initially struck about clashing part of kit
Buddy explains!

The straight part
We know that "Sitcom" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sitcom = hi.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 HI mean?
HI noun- The word "hi" used as a greeting.
- A friendly, informal, casual greeting said when meeting someone.
- An exclamation to call attention.
- Expressing wonder or derision.
- Very elevated; extending or being far above a base; tall; lofty.
- Relatively elevated; rising or raised above the average or normal level from which elevation is measured.
- Having a specified elevation or height; tall.
- Elevated in status, esteem, prestige; exalted in rank, station, or character.
- Of great importance and consequence: grave (if negative) or solemn (if positive).
- Consummate; advanced (e.g. in development) to the utmost extent or culmination, or possessing a quality in its supreme degree, at its zenith.
- (in several set phrases) Remote in distance or time.
- (in several set phrases) Very traditionalist and conservative, especially in favoring older ways of doing things; see e.g. high church, High Tory.
- Elevated in mood; marked by great merriment, excitement, etc.
- (of a lifestyle) Luxurious; rich.
- Lofty, often to the point of arrogant, haughty, boastful, proud.
- (with "on" or "about") Keen, enthused.
- (of a body of water) With tall waves.
- Large, great (in amount or quantity, value, force, energy, etc).
- (acoustics) Acute or shrill in pitch, due to being of greater frequency, i.e. produced by more rapid vibrations (wave oscillations).
- Made with some part of the tongue positioned high in the mouth, relatively close to the palate.
- Greater in value than other cards, denominations, suits, etc.
- (of meat, especially venison) Strong-scented; slightly tainted/spoiled; beginning to decompose.
- Intoxicated; under the influence of a mood-altering drug, formerly usually alcohol, but now (from the mid-20th century) usually not alcohol but rather marijuana, cocaine, heroin, etc.
- (of a sailing ship) Near, in its direction of travel, to the (direction of the) wind.