Take off warm Nairobi tunic, finally, after mile one (5)
I believe the answer is:
mimic
'take off' is the definition.
(I've seen this before)
'warm nairobi tunic finally after mile one' is the wordplay.
'finally' indicates one should take the final letters.
'after' means one lot of letters go next to another.
'mile' becomes 'm' (common abbreviation).
'one' becomes 'I' (Roman numeral).
The last letters of 'warm nairobi tunic' are 'mic'.
'm'+'i'='mi'
'mic' put after 'mi' is 'MIMIC'.
(Other definitions for mimic that I've seen before include "Imitate in order to ridicule" , "Imitate for humorous reasons" , "Imitate satirically" , "Ape" , "Caricature" .)