Ruin tent travelling in water, for example (8)
I believe the answer is:
nutrient
'water for example' is the definition.
(I know that water is a type of nutrient)
'ruin tent travelling' is the wordplay.
'travelling' is an anagram indicator.
'ruin'+'tent'='ruintent'
'ruintent' is an anagram of 'NUTRIENT'.
'in' is the link.
(Other definitions for nutrient that I've seen before include "Substance that provides nourishment, may be included in 6 Down" , "Substance that nourishes" , "Substance providing nourishment" , "Item of food" , "Good food" .)