Engineer repairs tip -- no sweat (12)
I believe the answer is:
perspiration
'sweat' is the definition.
('perspiration' can be a synonym of 'sweat')
'engineer repairs tip no' is the wordplay.
'engineer' is an anagram indicator.
'repairs'+'tip'+'no'='repairstipno'
'repairstipno' with letters rearranged gives 'PERSPIRATION'.
(Other definitions for perspiration that I've seen before include "Ninety nine percent of genius" , "is exuded" , "Sweat" .)