Mouldy buns leading to runs in a French holiday's discomfort? (7)
I believe the answer is:
sunburn
'holiday's discomfort?' is the definition.
(from too much sunbathing)
'mouldy buns leading to runs in a french' is the wordplay.
'mouldy' indicates an anagram.
'leading to' is a charade indicator (letters next to each other) (some letters go before or lead others).
'runs' becomes 'r' (cricket abbreviation).
'in' means one lot of letters goes inside another.
'a french' becomes 'un' ('a' in French).
'r' going within 'un' is 'urn'.
'buns' is an anagram of 'sunb'.
'sunb'+'urn'='SUNBURN'
(Other definitions for sunburn that I've seen before include "Redness caused by exposure to the source of heat" , "Painful browning of the skin" , "Effect of too much UV" , "Redness of the skin caused by solar rays" , "Reddening of skin" .)