Weighty pack for climbing soldiers (5)
I believe the answer is:
major
'weighty' is the definition.
Both the answer and definition are adjectives. Perhaps they are linked in a way I don't understand?
'pack for climbing soldiers' is the wordplay.
'pack' becomes 'jam' (synonyms).
'for climbing' is a reversal indicator (in a down clue, letters climb up).
'soldiers' becomes 'OR' (Other Ranks).
'jam' reversed gives 'maj'.
'maj'+'or'='MAJOR'
Can you help me to learn more?
(Other definitions for major that I've seen before include "Of considerable importance" , "Consecrate; thank" , "Main course" , "Word to describe key" , "Very significant - army officer" .)