Provided timers intermittently after gaffer loses head and becomes inflexible (8)

'becomes inflexible' is the definition.
The answer and definition can be both related to change as well as being verbs in their -s form.
Perhaps they are linked in a way I don't understand?

'provided timers intermittently after gaffer loses head' is the wordplay.
'provided' becomes 'if' (eg 'provided it's sunny' means 'if it's sunny').
'intermittently' means one should take alternating letters.
'after' means one lot of letters go next to another.
'gaffer' becomes 'boss' (synonyms).
'loses head' means to remove the first letter.
The alternate letters of 'timers' are 'ies'.
'boss' with its first letter removed is 'oss'.
'if'+'ies'='ifies'
'ifies' put after 'oss' is 'OSSIFIES'.

'and' acts as a link.

Can you help me to learn more?