The most common and most likely answer to this crossword clue is the 7 letter word CALLOUS
I've seen this crossword clue in The Times
C
A
L
L
O
U
S
More clues leading to the result CALLOUS
- Insensitive request for a ring — receiving different sort
- Hard decision to expel all but the last
- Heartless love, something superficial and hard about it
- Hard-hearted soprano on the radio
- A summons? Nothing to us, being hardened
- Emotionally hardened state with warped soul
- Visits from stand-by engineers, say, when temperature goes cold
- Label old American ‘heartless‘
- Summons? Nothing to us, being hardened
- Insensitive Opposition leader with American chasing visit
Buddy explains!

The straight part
We know that "Hard" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case hard = callous.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 CALLOUS mean?
CALLOUS adjective- Emotionally hardened; unfeeling and indifferent to the suffering/feelings of others.
- Having calluses.
- A hardened area of the skin (especially on the foot or hand) caused by repeated friction, wear or use.
- The material of repair in fractures of bone; a substance exuded at the site of fracture, which is at first soft or cartilaginous in consistency, but is ultimately converted into true bone and unites the fragments into a single piece.
- The new formation over the end of a cutting, before it puts out rootlets.
- A shining area on the frons of many species of Tabanomorpha (horse flies and relatives).