Growth in effort to become well-tanned? (7)
I believe the answer is:
swarthy
'become well-tanned?' is the definition.
I can't tell whether this defines the answer.
'growth in effort' is the wordplay.
I cannot really understand how this works, but
'growth' could be 'wart' (I've seen this before) and 'wart' is found in the answer.
'effort' could be 'shy' (shy is a kind of effort) and 'shy' is found in the leftover letters.
This accounts for all the letters.
This explanation may well be incorrect...
'to' acts as a link.
Can you help me to learn more?
(Other definitions for swarthy that I've seen before include "Dark-complexioned" , "Having a dark complexion" , "Dark complexioned" , "Dark-skinned" , "Dark skin" .)