Fastened it around man's head and measured duration (5)
I believe the answer is:
timed
'measured duration' is the definition.
'timed' can be an answer for 'measured' (timing is a kind of measuring). I am not certain of the 'duration' bit.
'fastened it around man's head' is the wordplay.
I cannot quite see how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found within the answer.
'man' could be 'ed' (short for Edward) and 'ed' is located in the answer.
The remaining letters 'im' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'and' acts as a link.
Can you help me to learn more?
(Other definitions for timed that I've seen before include "set against the enemy?" , "Measured the duration of" , "Measured performance" , "Scheduled" .)