Specialist from Switzerland mostly pleasant in greenish-blue (9)
I believe the answer is:
technical
'specialist' is the definition.
(I've seen this before)
'switzerland mostly pleasant in greenish-blue' is the wordplay.
'switzerland' becomes 'ch' (short for Confoederatio Helvetica, its Latin name).
'mostly' means to remove the last letter.
'pleasant' becomes 'nice' ('nice' is associated in meaning with 'pleasant').
'in' indicates putting letters inside.
'greenish-blue' becomes 'teal' (I've seen this before).
'nice' with its final letter removed is 'nic'.
'ch'+'nic'='chnic'
'chnic' inserted inside 'teal' is 'TECHNICAL'.
'from' is the link.
(Other definitions for technical that I've seen before include "Relating to mechanical art or applied science" , "Concerned with applied sciences" , "Industrial" , "drawing > fault > college > found after applying rules strictly" , "Requiring special knowledge to be understood" .)