The most common and most likely answer to this crossword clue is the 7 letter word REACTOR
I've seen this crossword clue in Financial Times
R
E
A
C
T
O
R
More clues leading to the result REACTOR
- Area covered by minister that gives power
- Minister welcoming a nuclear machine
- Incumbent of parish welcoming a source of energy
- Person who responds roughly to stern nurses
- Cleric guarding a nuclear structure
- Organise race to run power supplier
- Pile on ham
- Second note by Roy Scheider, say — one who responds
- Catholic moves to centre of God’s source of power
- Hurt perhaps following faithful instruction in nuclear facility
Buddy explains!
The straight part
We know that "Nuclear power source" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case nuclear power source = reactor.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 REACTOR mean?
REACTOR noun- A person who responds to a suggestion, stimulation or other influence.
- (industrial) A structure used to contain chemical or other reactions.
- A device which uses atomic energy to produce heat.
- A chemical substance which responds to the presence or contact with another substance.