Ferdinand possibly tense in unrest (4)
I believe the answer is:
riot
'unrest' is the definition.
(a riot is an instance of unrest)
'ferdinand possibly tense' is the wordplay.
'ferdinand possibly' becomes 'rio' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'tense' becomes 't' (abbreviation used in many dictionaries).
'rio'+'t'='RIOT'
'in' is the link.
Can you help me to learn more?
(Other definitions for riot that I've seen before include "unrestrained revelry" , "Disturbance of the peace by many" , "Debauchery" , "Civil disorder" , "Rowdy behaviour" .)