How many letters does the top answer for “the organic process of growing older and showing the effects of increasing age” have?

The most common answer is ageing (6 letters).

Crossword clue: the organic process of growing older and showing the effects of increasing age

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

ageing 6 letters wn-def

the organic process of growing older and showing the effects of increasing age

aging 5 letters wn-def

the organic process of growing older and showing the effects of increasing age